Optimizing Blockchain Based Smart Grid Auctions: A Green Revolution
aa r X i v : . [ c s . CR ] F e b Optimizing Blockchain Based Smart Grid Auctions:A Green Revolution
Muneeb Ul Hassan, Mubashir Husain Rehmani, and Jinjun Chen
Abstract —Integrating blockchain with energy trading is anew paradigm for researchers working in the field of smartgrid. In energy trading, auction theory plays an importantrole to ensure truthfulness, rationality, and to balance utilityof participants. However, traditional energy auctions cannotdirectly be integrated in blockchain based auctions due to thedecentralized nature. Therefore, researches are being carriedout to propose more efficient decentralized auctions for energytrading. Despite of all these advances, a greater standpoint thatis not well-highlighted or discussed in majority of proposedmechanisms is the integration of green aspect in these auctions.Since, blockchain is a novel paradigm to ensure trust but it alsocomes up with a curse of high computation and communicationcomplexity which eventually causes resource scarcity. Therefore,there is a need to develop and encourage development of moregreen auctions to carry out decentralised energy trading. In thispaper, we first provide a thorough motivation of decentralizedauctions over traditional auctions. Afterwards, we provide in-depth design requirements that can be taken into considerationwhile developing such auctions. After that, we analyse technicalworks that have developed blockchain based energy auctionsfrom green perspective. Finally, we summarize the article byproviding challenges and possible future research directions ofblockchain based energy auction from green viewpoint.
Index Terms —Smart Grid, Blockchain, Energy Auction, GreenEnergy, Green Auctions, Green Blockchain
I. I
NTRODUCTION
Till now, plenty of blockchain based auction approacheshave been developed by researchers and certain traditionalauctions such as double price, Vickrey, and first price auctions,etc, have been integrated into blockchain based energy trading,but this domain still faces certain issues and one of the majorissue is the scarcity of resources [1]. Usually, smart metersacting as blockchain nodes are computationally inefficientto carry out complex consensus, or sometimes, the storagecapability of certain nodes is not effective enough to storethe continuously generated data on ledger. Therefore, therearises a need to develop such type of computationally efficientmechanisms and architectures that can be integrated withdecentralized grid scenarios. Certain technical works havebeen carried out by researchers to address this problem, butit needs to be dealt on a larger scale and a foundation ofgreen auctions for blockchain based energy trading needs tobe implied to integrate blockchain technology to maximumpossible level.
M. Ul Hassan and J. Chen are with the Swinburne University of Tech-nology, Hawthorn VIC 3122, Australia (e-mail: [email protected];[email protected]).M.H. Rehmani is with the Munster Technological University (MTU),Ireland (e-mail: [email protected]).
In this paper, we present a comprehensive overview of waysthat can be adopted to optimize blockchain based energy auc-tions in order to overcome resource scarcity issues. Firstly, wediscuss basic fundamental technologies along with motivationof decentralized blockchain based energy auctions. Then weprovide a detailed discussion about design requirements thatwhat parameters can be incorporated in decentralized auctionsto enhance the green aspect in them. Afterwards, we carryout a thorough investigation over all the decentralized auctionapproaches proposed till now.. We mainly by discuss thetype of green parameters these works have used and whatothers aspects can be used in future to enhance the proposedmechanisms. Finally, we conclude the article by providing anin-depth insights about possible challenges and future researchdirections that can be critical for researchers working in thefield of decentralized energy trading.
A. Scope and Contributions of Our Work
Our article provides a thorough investigation over the topicof green auction design for blockchain based smart gridsystems. Certain key contributions of our work are as follows: • We discuss fundamental technologies and objectives thatcan play the part in designing of green decentralizedenergy auctions. • We highlight designs requirements that needs to be takencare of while developing infrastructure and algorithmsfor green auctions in blockchain based energy tradingdomain. • We survey the existing technical works and provide aviewpoint that what aspects can be improved in theseworks to make them more oriented towards green per-spective. • We summarize certain challenges, research directions,and open issues for researchers working in the field ofgreen auction design for blockchain based smart grid.
B. Comparison with Related Survey Works
Till now, several surveys have been published that havehighlighted various aspects of blockchain and smart grid [2]–[6]. For instance, authors in [2] provided a detailed overviewabout applications and potential trends regarding integrationof blockchain in smart cities. Authors surveyed the effectsof blockchain in smart grid, smart transportation, supplychain, and other similar domains. Similarly, another work thatthoroughly surveyed the integration of blockchain in futuresmart grid architectures have been carried out by authors in [3].Another work that highlights the privacy issues in blockchain
TABLE I C OMPARISON S UMMARY OF P REVIOUSLY P UBLISHED S URVEY A RTICLES WITH FROM P ERSPECTIVE OF C ONTRIBUTION AND S COPE . ✔ MEANS THE TOPIC IS COVERED , ✗ SHOWS THE DOMAIN IS NOT COVERED , AND ✽ MEANS THAT DOMAIN IS PARTIALLY COVERED .A CRONYMS : S
MART G RID A UCTIONS (SGA), G
REEN S MART G RID (GSG), G
REEN E NERGY (GE), B
LOCKCHAIN I NCENTIVES (BI),
AND T YPES OF B LOCKCHAIN A UCTIONS (T O BA).
ScopeMajor Domain Ref. Year Contribution Summary SGA GSG GE BI ToBABlockchain in SmartCities [2] 2019 A comprehensive review of application and potential ofblockchain in smart cities. ✽ ✗ ✽ ✔ ✽
Blockchain in SmartGrid [3] 2020 A brief literature review about integration of blockchainin future smart grid. ✽ ✔ ✔ ✽ ✗
Differential Privacyin Blockchain [4] 2020 An in-depth survey of integration of differential privacyin blockchain layers and applications. ✽ ✗ ✗ ✔ ✗
Smart Contract forBlockchain [5] 2020 A systematic review of usage of smart contracts inblockchain technology. ✗ ✗ ✗ ✽ ✽
P2P Energy Trading [6] 2020 An overview of P2P energy trading from perspective ofphysical & virtual layer. ✔ ✗ ✽ ✽ ✔
Green AuctionDesign forBlockchain basedSmart Grid
ThisWork 2020 A comprehensive analysis about design requirements andmethodologies for overcoming resource scarcity in orderto develop green auctions for blockchain based smartgrid energy trading. ✔ ✔ ✔ ✔ ✔ and their countermeasures using differential privacy have beenpresented in [4]. Similarly, the possible use cases and thesignificance of smart contracts in blockchain scenario hasbeen extensively reviewed by authors in [5]. One more workthat provide in-depth insights about peer-to-peer (P2P) energytrading in physical and virtual layer have been presented in [6].Complementary to all these surveys, our work highlight theaspect of green auction design in blockchain based energytrading. We provide extensive design requirements along witha thorough analysis about all technical works that proposeddecentralized energy auctions. To the best of our knowledge,this is the first article that highlights the aspect of green auctionin blockchain based energy trading in detail from a designviewpoint.
C. Paper Organization
The remainder of the article is organized as follows: Section2 provides motivation and fundamentals of green auctionsin blockchain based smart grid, Section 3 highlights designrequirements that should be incorporated to design greenauctions. Section 4 surveys existing technical works alongwith providing the insights that how these works can beimproved to overcome resource scarcity in future. Section 5highlights significant challenges and future research directionsfor researchers interested to explore this field further. Finally,Section 6 concludes the article.II. F
UNDAMENTALS OF G REEN A UCTIONS FOR B LOCKCHAIN BASED E NERGY T RADING
Game-theory and blockchain are playing a significant rolein development of modern energy auctions. In this section,we first provide the motivation of such auctions and thenwe discuss types and objectives of blockchain based energytrading.
A. Motivation of Blockchain based Energy Auctions
Smart grid energy trading is advancing rapidly and auctionmechanisms are playing a vital role in this development. Cer-tain parties such as smart homes, prosumers, energy buyers, grid controller, etc., are involved in these auctions, therefore, itis important to incentivize each participant in the best mannerin order to maintain their motivation level [7]. These energyauction mechanisms ensure truthfulness, but due to centralentity, they lacks a perception of trust among participants. Inorder to overcome this issue of trust, decentralized blockchaintechnology came up as a rescuer. In blockchain based auctionmechanisms, all blockchain nodes have a copy of distributedledger, so no specific node have control over the whole data.This decentralized storage provides transparency and ensuresthat none of auction record can be altered once it gets recordedbecause everyone have a copy. Moreover, this record is main-tained and updated via strong consensus mechanism that is iscarried out among mining nodes, which enhances the trust abit further. Due to these aspects, plenty of researchers havedirected their research towards development of blockchainbased energy auction and it is being considered as a futureof energy trading in modern smart grid [8].
B. Types of Auctions in Green Smart Grid
Plenty of researches have been carried out in the fieldof decentralized blockchain, however, considering a broaderperspective, the two most used auctions types on blockchainbased energy auctions are double auctions and Vickreyauctions. Apart from these two major auctions, certain otherauction strategies that work over the principal of first priceauction have also been formulated by researchers in the fieldof blockchain based energy trading. We categorize theseauctions under the category named as “Conventional FirstPrice Auction”. In this section, we define the basics andpricing rule of these auction mechanisms from perspectiveof decentralized energy trading. However, before movingtowards different types of auctions it is important to knowcertain base terminologies that are commonly used in auctionssuch as bidder, bid, ask, pricing rule, etc, which are discussedin Table II.
TABLE II B
ASIC T ERMINOLOGIES U SED IN E NERGY A UCTIONS ALONG WITH THEIR D EFINITIONS
Terminology DefinitionAllocation Rule
A pre-defined rule which is used to find the winner of an auction process.
Bidder
A bidder is the participant who shows interest in purchasing a specific energy slot by putting forward somevaluation for the slot.
Energy Slot
A specific time slot during which a specified amount of energy is available at sellers.
Hammer Price
Final price of a commodity selected by auctioneer or algorithm.
Pricing Rule
A pre-defined rule which is used to determine the final price of auction process.
Payment Method
A pre-decided method to pay for purchased energy (it could be on-chain and off-chain).
Seller
Seller is the entity who owns the energy and is willing to sell the stored energy in a specific time slot.
Valuation
A monetary value for any specific time slot which buyers are willing to pay (this could be public or private).
1) Double Auction:
The functioning of double auctionmechanism lies in the phenomenon that both buyers andsellers are bidding for the nominated energy slot. Energybuyers tends to get the lowest price, while on the other handprosumers or energy sellers try to sell the energy in themaximum possible price. Furthermore, buyers compete withother buyers to purchase energy for a determined slot andsellers compete with other sellers to sell energy in order toenhance their utility. In this way, an energy demand-supplycurve is formed which is used to predict the outcome andmarket clearing price (MCP) of energy auction. Readersinterested to find more detailed discussion about demand-supply curve in double auction can study the work carriedout by Zhang et al. in [9]. In traditional energy auction, thefinal payment/MCP is calculated by centralized auctioneer viaabove defined matching process. However, in decentralizedblockchain based energy auctions, the complete process iscarried out in a decentralized manner, so every buyer andseller can view and verify the demand-supply curve to ensureauthenticity. After finalizing MCP, the winning buyers pay theamount they bid ( P j ( S ) = b j ) for the specified slot, which isalso known as buyers payment.
2) Vickrey Auctions:
Vickrey auctions lies in sealed-bidauction types in which buyers do not share their valuation/bidspublicly and instead submit their valuations to some trustedauctioneer. Generally, Vickrey auctions are divided into twofurther types named as k-th-price auction and Vickrey-Clarke-Groves (VCG) auction. a) K-th-price Auction:
In this type of auction, the winneris the one who pays the highest bid. However, the final price p j depends upon the value of k th bid, and this value of k determined before starting of auction. For instance, in Vickreysecond price auction ( k =2), the highest bidder wins the energyslot, however, it will pay the second highest bid. b) VCG Auction: VCG auction is a generalized form ofVickrey auction, in this auction, buyer pays the amount ofharm it causes to other buyers due to its presence.E.g., ina decentralized VCG auction, N energy buyers submit theirvaluations V = { b , b , ...b N } for a specific energy slot ( s ) tothe network for winner determination and price section. Aftercompletion of the specified time along with reception of allbids, the VCG mechanism is used to determine the final price P = { P , P , ...P N } and allocation vector for the bidders. Theprice of each energy buyer is determined on the basis of harm its valuation causes to other buyers, which is determined byusing following formula: P i ( B ) = max b ∈ V X k = j B k ( b ) | {z } ( A ) without winner k − X k = j B k ( b ∗ ) | {z } ( B ) with winner k (1)In the above equation, b ∗ is the output of winner chosen withrespect to highest bid, k works as an iterative parameter whichiterates through all submitted bids except for the winning bidfrom bidder j . In equation, part (A) is the accumulated sumof all the bids without participation of winner j , while part(B) is the accumulation of bids including the winning biddersbid.
3) Conventional First Price Auctions:
Apart fromtwo major auction types, other auctions in smart gridenergy trading can be categorised under the category ofconventional/traditional first price auctions. In conventionalfirst price auctions, highest bidder wins and pays the biddingprice for the energy slot. However, the steps to carry outauction can vary. For instance, in sealed bid first priceauction, all bids are hidden. Contrarily, in open-cry firstprice auction all bids are public at the time of auction. Adetailed discussion about integration of first price auctions ingreen blockchain based energy trading has been provided inSection. IV-C.
C. Objectives of Energy Auctions
Auction theory in energy trading is used to get maximumbenefits from auction processes which in turn benefits allparticipants of auction including buyers, prosumers, maingrid, etc. Every auction mechanism have some objectives,for instance, some provide maximum social welfare, whileother incentivize sellers, etc. However, three objectives canbe defined as universal auction objectives which usually allauction mechanisms tries to achieve are as follows:
1) Social Welfare Maximization:
In a decentralized energyauction, social welfare can be termed as sum of individualutilities of all participants, and individual utility is the amountof benefit every participant gets while participating in theauction process. For instance, a buyer valued an energy slotfor $50 and the final price he paid after auction calculationis $40, then the utility of buyer ( U b = $50 − $40 ) willbe $10. Similarly, the difference between final price and ask of an energy seller is termed as utility of prosumer orenergy seller. A utility value greater than zero shows thatthe profit is gained by the particular participant. In this way,the summation of utilities of all participants is said to besocial welfare of the network [10]. Therefore, energy auctionmechanism are designed in such a manner that they maximizethe social welfare of the whole network.
2) Individual Rationality:
An energy auction process willbe individually rational when each participating buyer andseller have non-negative utility at the end of auction. It is doneby developing energy auctions in such a manner that buyersand sellers are charged and paid exactly according to their bidsand asks respectively [11]. Therefore, it is important to keepthe aspect of individual rationality as a significant parameterwhile development of energy auctions.
3) Equilibrium:
Equilibrium in auctions is a concept ofgame theory which is used to analyse the behaviour of par-ticipating buyers and sellers, which is further used for variousstatistical processes such as market analyzation, etc [12].Multiple equilibrium types have been developed by researchersto maximize benefit of auction such as Bayesian equilibrium,mixed-strategy equilibrium, correlated equilibrium, etc. How-ever, the most commonly used equilibrium solution in energybased auctions in Nash equilibrium, which makes sure thatnone of the participant can get more benefit by changingtheir playing strategy unilaterally provided that the strategiesof other participants remains constant. While developing anenergy auction, researchers aim to achieve the most desiredequilibrium type by developing incentive strategies accord-ingly.Apart from these three major objectives, certain other ob-jectives that come up from perspective of blockchain basedenergy trading can be termed as follows:
4) Smart Contract:
Smart contract can be termed as a fixedset of code which executes itself when specified conditionsmet [5]. In case of blockchain based energy auctions, smartcontract is usually used to perform allocation and pricing inan efficient manner. Smart contract is stored on blockchainand they can be executed at the time of need. Smart contractprovides the flexibility to its users that they can choosebetween multiple operation at the time of auction. For instance,various of energy efficient auctions can be adopted on asingle blockchain network by just varying the smart contract.Contrarily, in a hardcoded blockchain code, the users do nothave this feature. Therefore, majority of modern blockchainbased energy auctions are integrating smart contract in theirwork.
5) Transaction Cost Enhancement:
Another objective thatblockchain based energy auctions are trying to meet is toreduce to the size of auction transactions to as much degreeas possible. This is being done in order to overcome theresource scarcity issue of blockchain. Since blockchain is adecentralized distributed ledger and every node has a copy ofthe ledger, but all blockchain nodes do not have that much ofliberty to store millions of records [13]. Therefore, in orderto meet the need of ever-growing auction data, research isbeing carried out to reduce the transaction size in order to save transaction storage cost. This aspect of transaction costenhancement is further elaborated from perspective of energyefficient storage in Section. III-D.
6) Enhancing Energy Demand and Consumption:
Efficientenergy utilization plays an important role during developmentof blockchain based energy auctions because it determines theeffectiveness of any decentralized auction mechanism [14].Within the domain of efficient energy utilization, researchersespecially focus over two aspects. One from perspective ofmeeting energy demand of an area/suburb, and second tomaintain a healthy ratio between consumption of energywith respect to its generation from renewable resources. Thisobjective of efficient energy usage is further divided to developvarious design requirements in energy auctions, which isdiscussed in Section III.III. D
ESIGN R EQUIREMENTS FOR G REEN A UCTIONS IN B LOCKCHAIN BASED S MART G RID E NERGY T RADING
In this section, we highlight certain design requirementswhich can be considered while developing auction mecha-nisms in order to enhance them to be greener from communi-cation, computation, and energy perspective.
A. Energy Efficient Blockchain Communication
Since blockchain works over the phenomenon of decentral-ized distributed ledger, therefore, every node of blockchainwill be connected with each other via some wireless technol-ogy. So, every new update in the network is broadcast to allother participating nodes. This redundant retransmissions andbroadcast causes certain communication related issues such ashigh energy usage, channel attenuation, noise, etc [15]. Certaincommunication strategies and mechanisms have been used byresearchers to overcome communication cost, for instance,usage of bloom filters, push and announce requests, flooding,gossiping, etc [16]. However, research has not been carried outfrom perspective of sharing auction data in the most proficientmanner.
Discussion:
Overcoming communication cost is one of themost significant challenge in blockchain systems because ofredundant transmissions in case of every new update. Plentyof aspects in blockchain based auctions can be enhancedto perform energy efficient communication. Firstly, reductionof string length in auction message broadcast can play asignificant role. For instance, finding the best combination ofdata that conveys all parametric requirements of auction canbe found. Secondly, usage of green communication mecha-nisms which either use minimum energy or use the availablespectrum in an efficient manner needs to be taken care of. Forexample, blockchain nodes can be converted to cognitive radionodes in order to utilize spectrum efficiently.
B. Energy Efficient Consensus for Blockchain
Consensus mechanism is considered to be the heart of anyblockchain network because carrying out decentralized con-sensus was the starting point which distinguished blockchainfrom other distributed computing systems. However, the first blockchain consensus mechanism (proof of work (PoW))require miners to solve computationally complex puzzle tomine the block, which require very high computational power.Afterwards, certain other mechanisms such as proof of stake(PoS), proof of burn (PoB), proof of Elapsed Time (PoET),etc, have been developed for different applications.
Discussion:
Consensus mechanisms play an integral partin sustainability of blockchain network, but development ofa consensus mechanism that incorporate various parametricaspects of blockchain based smart grid auctions needs to beconsidered. Authors in [17] developed an energy orientedconsensus for P2P energy trading which can be consideredas a first step toward green consensus design purely forenergy trading. However, there is still a large room whichcan be explored, and researches can be carried out in plentyof directions of green consensus design. For instance, onedirection could be to develop more energy efficient consensusthat is purely oriented for blockchain based auctions. Anotherapproach could be to develop such consensus mechanismswhich work over energy generated from renewable energyresources (RERs). Overall, we believe that green consensusdesign can serve as a prospective direction to make blockchainbased auction greener.
C. Energy Efficient Auction Design
As auction is the core component of blockchain based smartgrid auctions, so if one wants to enhance the performance ofsuch mechanism from green perspective then the first thing toconsider is to enhance the performance of auction mechanismin a way that it lies under the umbrella of energy efficientauction.
Discussion:
As discussed in earlier sections that auctiontheory is a pretty old domain of statistics, however, researchesare still being carried out to develop energy efficient auctions.For instance, single unit first price auctions carried out for500 energy slots and 500 bidders will take far pretty lesscomputational resources as compared to VCG auction carriedfor similar number of bidders and sellers. It is because incase of VCG auction one has to compute loss caused byeach buyer to all other buyers. However, the game-theoreticaspects such as truthfulness, rationality, etc, of VCG auctionare more dominant over first price auction. Therefore, whiledevelopment of energy auctions for blockchain based smartgrid, researches need to consider the aspect of energy andcomputational consumption along with providing rationality,truthfulness, and equilibrium.
D. Energy Efficient Auction Data-Storage (On-Chain & Off-Chain)
Blockchain data storage has been in discussion since theadvent of blockchain because data of blockchain is increasingwith the addition of every new blocks in the ledger. This isrequired to ensure trust, however, certain nodes are not capableof storing massive amount of data. Therefore, researchesare focusing over both type of storages, on-chain and off-chain [18].
Discussion:
From perspective of blockchain based smart grid auction, both of the data storing approaches can beconsidered as both have their pros and cons. For instance,if one store complete auction and trading data on-chain, thenthe nodes (especially smart meters) needs to have high storagecapability to store it. Contrary to this, if the complete datais stored off-chain then one gets deprived of various usefuladvantages of blockchain such as trust enhancement, etc.Therefore, one need to consider both pros and cons of eachstrategy while development of auction. There are plenty ofprospective directions for this requirement, for instance, onecan store only transaction history on smart meter nodes andstore the rest of data in external database. Another direction isto use external storage for blockchain nodes. Similarly, anotherdirection could be to optimize auction data in such a way that itutilize minimum storage, for instance, removing excessive datawhich might not be required for any future usage. Consideringthese aspects, it can be said that storage mechanisms needsto be modified from perspective of blockchain based energyauctions.
E. Green Auction Data Analytics for Future Operations
Data analytics is not directly linked with auction design,but it definitely has links with the stored data. As discussed inthe above subsection that green methods needs to be adoptedfor auction data storage, similarly, the integration of greendata analytic strategies while analysing auction data can playa major role in development of a complete green and costfriendly system [19].
Discussion:
Data analytic plays a critical role in controllingoverall cost of network because of the reason that majorityof auction data is collected for the purpose future forecasting.E.g., how much energy is generated from a specific resource,or how much energy is purchased in a specific suburb, etc.Therefore, development of such data analytic mechanismswhich are energy and resource efficient needs to be considered.One direction could be development of innovative architecturethat utilizes energy resources in the most efficient manner,another direction could be to design such data processingframeworks which consumes minimum resources to analysemaximum data, another direction could be integration of RERsbased energy in analytics, etc. So, strategies needs to bedeveloped and action needs to be take in direction of greendata analytics for blockchain based smart grid auctions.
F. Energy Harvesting Nodes for Blockchain Auction Network
Harvesting energy from various environmental factors topower electronic devices is one of the most promising strategyto eliminate battery dependency. In order to so, more than 5000different research works have been carried out till now [20].However, harvesting energy for blockchain nodes is still a newdomain and very minimal work has been carried out in thisdirection. Although, it is a new domain, but this concept ofenergy harvesting blockchain nodes have strong roots and canhelp in a much deeper manner towards development of greenblockchain based smart grid auctions.
Discussion:
In order to incorporate the concept of energyharvesting in blockchain based energy auctions, firstly, it is important to analyse and identify potential deployment places.For instance, one potential framework could be to integratethe concept of energy harvesting with blockchain based smartmetering nodes, so that these nodes could power themselves atthe time of auction and consensus process. Another possibledirection could be to integrate energy harvesting only withcontrolling/mining nodes which are responsible to carry outextensive computational tasks. The second important aspectwhile integrating energy harvesting phenomenon in blockchainbased auction is to figure out optimal material and manufactur-ing details for harvesting devices. For example, it is importantto evaluate that which specific type of energy harvester suitsthe best? and what is the best framework to design them up?Similarly, the aspect of cost can also not be ignored whiledesigning energy harvesting devices for blockchain basedauction systems. However, it is worthwhile to mention thatthe aspect of integration of energy harvesting with blockchainbased energy auctions could play a significant role if its carriedout in a proper direction. Because it can save a massive amountof energy which is consumed during mining, consensus, andother blockchain processed. Therefore, integration of energyharvesting in blockchain based smart grid nodes is a muchneeded approach in future, as it will help to improve self-sustainability of blockchain network.
G. Green Energy Scheduling for DSM Enhanced Auctions
Demand side management (DSM), which is used to controland balance demand and supply of energy is an integral partof modern day smart grid system. Previously, only shapingthe energy usage was considered the only option to managepeak-to-average ratio (PAR), however, nowadays it has beenproved by research that it is not the only solution and plentyof other mechanisms can also play their role in DSM [21].Researches have been carried out and efficient energy storage,scheduling, and trading is considered to be one of the mostpromising ways to reduce PAR in areas where there is highratio of prosumers.
Discussion:
Scheduling green renewable resources-basedenergy is also in discussion due to increased interest in efficientDSM. Energy is being scheduled by user in order to sell themat the time of high need. This trading is being carried outvia blockchain based auction systems, which are responsibleto provide optimal revenue in return of energy. Scheduledenergy is a great way to enhance green aspect and to reducethe probability of blackouts in the area, because the greenenergy can be stored and used at the time of need. In orderto understand it further, lets take the example of a user Xwhich has a specified amount of energy stored in the batteriesthat he wants to sell. So, instead of selling the energy straightaway it can auction for a specified time slot when energydemand is considerably high. Similarly, another prosumer canpurchase and store energy at the time of low prices and cansell at the time of need and all this can be done via P2Penergy trading carried out via blockchain. An interesting workin this direction has been carried out by authors in [22], whodeveloped a grid influences strategy for this process. However,this aspect of green energy scheduling for blockchain basedenergy trading needs more exploration in future. IV. B
LOCKCHAIN BASED A UCTION A PPROACHES FOR G REEN S MART G RID
Various technical works integrating different types of auc-tions strategies in blockchain based energy trading have beencarried out by researchers till now. On a broader scale, theseworks can be categorised in to three major categories: 1)double auctions 2) Vickrey Auctions 3) conventional firstprice auctions. We discuss a comprehensive overview of thesetechnical works from perspective of green design requirementsin this section. From perspective of design requirements,certain technical works tried to address one or more designrequirement in order to enhance the green aspect in theirdecentralized energy auction. In this section, we provide anin-depth analysis of these works from green perspective. Apartfrom discussion, a detailed table highlighting the contributionand addressed design requirements, and other technical param-eters have been presented in Table. III.
A. Double Auction
In a double auction mechanism, buyers and sellers submittheir bids and asks in order to find a hammer price, which isfurther used to determine the total number of sold energy slots.Firstly, sellers submit their asking price which is arrangedin an ascending order, afterwards, buyers submit their bids,which is arranged in a descending order. Once asking priceand bids are collected, then the aggregated curves for demandand supply are generated and mapped over each other tofind the intersection point. The intersection point is usedto determine the hammer price of double auction, which isfurther used to find out the winning buyers and sellers [47]. Adouble auction mechanism is said to be incentive-compatible,when by acting on the preferred bids and asks, each buyer andseller gets their best outcome. Therefore, while developingdouble auction based energy trading mechanisms, researcherstend to integrate the functionality of incentive compatibilityin their mechanisms. We divide this section of double auctioninto four sub-sections on the basis of incorporation of greendesign requirements in these works.
1) Efficient Auction Mechanism Design:
Enhancing effi-ciency of double auction by reducing the convergence time is acritical step towards designing of green double auctions for de-centralized smart grids. Till now, two works have been carriedout by researchers that focused over reducing the iteration ofenergy auctions in order to converge them quickly as comparedto traditional double auction. One such work in the directionof efficient auction design has been carried out by Kang etal. in [23], where authors work over enabling P2P energytrading for grid connected EVs using efficient double auctionmechanism. Authors used the phenomenon of flag and triggerto solve the complex iterative problem of double auction in anoptimal way. The proposed mechanism uses less iteration toconverge, which in turn save excessive usage of energy duringiteration process. Furthermore, the work also used consortiumblockchain to overcome computational scarcity issue for thenodes which do not have significant computational resources.Another work discussing quick converging double auction
TABLE III T ECHNICAL W ORKS IN B LOCKCHAIN BASED G REEN S MART G RID A UCTIONS .A CRONYMS : S
OCIAL W ELFARE (SW), I
NDIVIDUAL R ATIONALITY (IR), E
QUILIBRIUM (EQ), T
RANSACTION C OST (TC), E
NERGY C ONSUMPTION (EC), E
NERGY D EMAND (ED), S
MART C ONTRACT (SC), N OT S PECIFIED (N/S).
Auction Objectives MetAuctionType AddressedGreen Issue Ref. Major Contribution Type of DesignRequirements Met BlockchainType ConsensusMecha-nism SW IR EQ TC EC ED SC
EfficientAuctionDesign [23] Localized P2P energy tradingfor grid connected EVs. • Auction IterationReduction • Reductionin Energy Consumption Consortium PoW ✔ ✔ ✔ [1] Quick converging P2Pauction for smart grid. • Auction Convergence• Energy Loss Reduc-tion • ComputationOverhead Public PoW ✔ ✔ ✔ ✔ ✔ ✔ [24] Multi-tier energy auctions fordistribution grids. • Scalability• Computational Cost Public BusinessDriven ✔ ✔ ✔ ✔
Communica-tion &ComputationCostReduction [25] Field implementationof energy market inSwitzerland. • CommunicationCost Reduction viaTendermint Private(permis-sioned) Tendermint ✔ ✔ ✔ [26] Proposed three approachesfor energy trading. • ComputationEfficiency Public PoA ✔ ✔ ✔
Transaction& DataStorageEfficiency [27] Multi & internal micro gridenergy trading. • Distributed DataStorage • Reduction inTransaction Volume Public N/S ✔ ✔ ✔ ✔ ✔
DoubleAuctions [28] First price, time first baseddouble auction for microgridenergy trading. • ImprovingTransaction Efficiency Consortium PBFT ✔ ✔ ✔ [29] Power flow & multilateralenergy trading via Ethereumblockchain. • Detecting OverlimitPower-Flow to ManageEnergy Private PoW ✔ ✔ ✔ [30] Decentralized load balancingfor P2P energy trading. • P2P Energy CostReduction Public N/S ✔ ✔ ✔ ✔ [31] Decentralized load balancingvia energy markets. • Managing & TradingEnergy Locally Public Tendermint ✔ ✔ ✔ ✔ ✔ [32] Charging power quota basedenergy trading. • Charging StationsSettlement via PowerQuota Private N/S ✔ ✔ ✔ ✔ [33] Selfish & helpful biddingstrategy for residential DERs. • Peak Load Reduction PBFT PBFT ✔ ✔ ✔ ✔ ✔
EnhancingEnergy Cost [22] Grid influenced P2P Energytrading via Stackelberggame. Reduction in PeakDemand Public N/S ✔ ✔ ✔ ✔ ✔ ✔ [34] Energy exchange andsettlement procedures forenergy trading. • Balancing EnergyConsumption &Production Ratio Public PoS ✔ ✔ ✔ ✔ ✔ ✔ [35] Decentralized localenergy trading to enhancesustainability. • Enhancing LocalTrade to Prevent EnergyLosses Public PoI ✔ ✔ ✔ [36] Hybrid P2P and P2G energytrading. • Cost Reduction viaHybrid Energy Trading Public N/S ✔ ✔ ✔ ✔ [37] Reward enhancing transactiveenergy auctions. • Local Energy TradingEnhancement Public PoW ✔ ✔ ✔ ✔
VickreyAuctions
EnhancingEnergy Cost [38] Differentially privatedecentralized microgridauction. • Energy Reduction Consortium PoW ✔ ✔ [39] Quasi-ideal P2P transactiveenergy trading. • Managing MarketSurplus Energy Public PoC ✔ ✔ ✔ ✔ [40] Multi-microgrid based energytrading. • Efficient ArchitectureDesign Public N/S ✔ ✔
EnhancingEnergy Cost [41] Transactive energy exchangefor EI based blockchain. • Enhancing EnergyManagement via EIConcept Private(permis-sioned) PBFT ✔ ✔ ✔ ✔ [42] Practical implementation ofdecentralized energy trading. • Cost Reduction Public N/S ✔ ✔
Transaction& DataStorageEfficiency [43] Game-theoretic frameworkfor V2G network. • Tx Throughput• Scalability Public IoTA ✔ ✔ ✔ ✔ ✔ ✔ [44] Sealed auction transactionsfor V2G network. • Transaction Matching& Convergence Public PoA ✔ ✔ ✔ ✔
Conven-tionalFirstPriceAuctions [45] Blockchain + IFPS storagefor energy trading. • Enhancing DataStorage Public Multiple ✔ ✔ ✔ ✔ ✔ [46] DSM enhancing grid optimalauction. • ScalabilityEnhancement Public N/S ✔ ✔ ✔ ✔
EfficientAuctionDesign [44] Sealed auction transactionsfor V2G network. • Transaction Matching& Convergence Public PoA ✔ ✔ ✔ ✔ have been presented by authors in [1]. Authors designed amechanism via which majority of energy demands can be metin short number time, which in turn reduces the convergingtime for double auction. Moreover, authors also enhancedenergy losses and computation overhead by motivating peersto trade energy locally.
2) Communication & Computation Cost Reduction:
Pro-viding efficient communication and computation has alwaysbeen an important objective while development of decentral-ized energy auctions. In order to do so, certain research havebeen carried out by researchers, one such work to provideenergy efficient computation for multi-tier auction distributiongrids have been carried out by authors in [24]. Authors useda business driven consensus mechanism to enhance computa-tional factor along with providing a more scalable blockchainmodel for secure energy auctions. Similarly, from perspectiveof field implementation, a detailed study on blockchain basedenergy market of Switzerland has been presented by authorsin [25]. The work discussed reduction of communication andcomputation cost by using Tendermint consensus instead oftraditional consensus protocols. Another similar work thattargets to reduce computational scarcity in blockchain basedauctions have been carried out by authors in [26]. The workproposed three energy trading approaches for blockchain basedsmart grid and compared them on the basis of cost and effec-tiveness. Similarly, the authors also provided the comparisonof these approaches from perspective of clearing price andclearing quantity.
3) Transaction & Data Storage Efficiency:
Storing andmanaging auction data in an efficient manner is one majorchallenge that blockchain based energy trading nodes are fac-ing right now because of the distributed nature of blockchain.Since blockchain works over the phenomenon of distributedledger, therefore, every new transaction is stored over thisledger. Considering the resource capacity of participating en-ergy nodes, it is important to design such auction mechanismswhich utilize minimum space while storing transaction data.On such work discussing an important aspect of dealingwith energy transaction from perspective of both internal andmulti-microgrids have been addressed by Zhao et al. in [27].Authors enhanced distributed data storage along with reductionin transaction volume in order to provide more sustainableblockchain network from the point of view of our designrequirement of efficient data storage. Another work to improvetransaction efficiency by using first price and time-baseddouble auction for blockchain based energy trading have beencarried out authors in [28]. Authors evaluated the phenomenonof enhanced of transaction efficiency at difference pointsand claimed that the proposed mechanism provides energyefficiency alongside providing transaction storage efficiency.Furthermore, the work also used consortium blockchain PBFTconsensus to reduce computational consumption.
4) Enhancing Energy Cost:
Among all design require-ments, one of the most critical design requirement whiledeveloping of double sided energy auctions is to reduce energyconsumption as much as possible. Researchers are doing thisvia various approaches, some worked over motivating users totrade energy locally, while others proposed hybrid mechanisms for this trade. In this section, we summarize all these fromperspective of their particular contribution to reduce energyusage at grid or user level in blockchain based energy tradingauctions. First work that evaluated power flow and multilateralenergy trading via Ethereum have been carried out by Jin etal. in [29]. One of the major contribution of authors inthis work from green perspective is detection of overlimitpower flow to reduce energy losses. Similar to this, twoworks focusing over decentralized load balancing via energyauction have been carried out by authors in [30], [31]. In [30],authors reduced P2P energy trading cost by proposing anauction mechanism which works over three layered blockchainarchitecture including application, virtual, and physical layer.Similarly, in [31], authors proposed an approach to balancerenewable energy generation locally via novel auction marketdesign.A unique work from perspective of power quota based energyauction over blockchain have been presented by Ping et al. in [32]. Furthermore, authors worked over development ofenergy efficient mechanism for charging station settlement.A work that analyses the behaviours of selfish and helpfulbuyers on residential RER auction have been presented in [33].Authors developed efficient bidding based MCP managementsystem which enhances DSM by reducing peak load from res-idential houses. Similarly, an extensive theoretical contributionutilizing the benefits of Stackelberg game in blockchain baseddouble auction have been presented by authors in [22]. Authorsproposed a grid-influenced game-theoretic approach to reduceenergy usage in peak hours which in turn provides efficientDSM. Similarly, a works on energy exchange and settlementprocedures have been carried out by Han et al. in [34]. Authorsproposed a blockchain based trading architecture that worksover execution of smart contract in order to balance energyconsumption and production.A similar work focusing over decentralized energy trading toenhance sustainability of smart grid have been carried outby authors in [35]. Authors motivated local prosumers andbuyers to carry out local trade in order to prevent surplusenergy losses. Another work focusing over hybrid P2P andP2G energy trading blockchain based double auction havebeen presented by researchers in [36]. In this work, au-thors focused over cost reduction by motivating the trend ofhybrid energy trading rather than just P2P energy trading.Apart from traditional double auction, a work focusing overBandit learning based energy trading have been presentedby researchers in [37]. The work focused over using Banditlearning based double auction to enhance reward in transactiveenergy auctions in order to motivate maximum sellers to tradeenergy to the decentralized market.
B. Vickrey Auctions
Vickrey auctions are usually used to maximize socialwelfare of all participants, because they provide a stronggame-theoretic guarantee that every participant will havea non-negative social welfare at the end of the auctionprocess [48]. In blockchain based green energy auctions,Vickrey auction has been applied in two technical works and in both of them they applied VCG auction, whichis an advanced form of Vickrey second price auction. InVCG auction, highest bidder wins but pays the harm itspresence have caused to other participating bidders. A detaileddiscussion about theoretical aspect of VCG auction is out ofscope of this article, interested readers are suggested to gostudy the work in [39]. Moreover, both of the works applyingVCG auction in blockchain based energy trading focusedover reduction of energy cost and consumption to enhancethe green effect in trading.
1) Enhancing Energy Cost:
The first work integrating dif-ferential privacy, VCG auction, and consortium blockchain fordecentralized energy auctions have been carried out by authorsin [38]. The given work enhanced buyers and sellers utilityalong with providing privacy preservation via differentialprivacy guarantee. In order to preserve energy and communica-tion cost of all participating nodes, authors proposed the usageof consortium blockchain instead of public blockchain. Byusing this blockchain network, only the selected participantswill be able to take part in consensus, which in turn save thecomputation cost for casual smart metering nodes. Anotherwork over VCG auction based energy trading have beencarried out by authors in [39]. The authors worked over quasi-ideal P2P transaction energy trading mechanism in order tomanage market surplus energy via VCG auction mechanism.Authors proposed a mechanism to handle four types of energytrading mechanisms in parallel, via which users can tradein a parallel manner according to different type of energyrequirement.
C. Conventional First Price Auctions
Apart from two major auction types (which are discussedin above subsections), certain other works used various otherauctions or similar trading approaches such as ascending priceauction, message broadcasting base auction, Ausubel clinchingauction, etc. It is important to note that all of these works chosehighest bidder as a winner. Based upon this understanding,we named the section as ’Conventional First Price Auctions’.The works in this section can further be categorized intothree categories on the basis of integration of green designrequirement, which are as follows:
1) Enhancing Energy Cost:
In first price auction mecha-nisms, one of the major focus of researchers is to enhanceenergy cost in order to make sure that the proposed mechanismis suitable for energy constrained blockchain nodes. Plenty ofworks have been carried out to overcome this energy scarcity,one such work functioning on unified weight clearing to selecthammer price for energy slots have been proposed by Li et al. in [40]. Authors designed an energy efficient architecture forsmooth energy trading in multi-microgrid scenario. Similarly,another work that provides a thorough comparison betweenthree auction strategies on the basis of tokens, supply-demandregulation, and energy consumption has been presented byauthors in [41]. The work further used the concept of energyInternet with transactive grid to trade energy in local marketsin order to prevent excessive energy losses. Similarly, another work that used traditional first price auction along with pro-viding the practical implementation of decentralized energytrading have been presented in [42]. Authors presented anextensive case study of practical implementation that ensuredreduction of energy cost as compared to traditional blockchainimplementation.
2) Transaction & Data Storage Efficiency:
Another greendesign requirement that have been addressed in first priceenergy auction works is enhancement of transaction sizeand data storage. A very detailed work from perspective ofenhancing Tx throughout and scalability of blockchain basedgame-theoretic ascending price auction have been presentedby Hassija et al. in [43]. Authors first provided a thorougharchitecture for grid-connected EVs energy trading, and thenevaluated the proposed model by showing that the model en-hanced transaction throughput and blockchain scalability. Onesignificant work that integrated IPFS storage with blockchainof manual E-auction based energy trading have been presentedby authors in [45]. The work developed a novel system modelto show the interoperability of IFPS storage with blockchain,and afterwards authors provided simulation based experimentsto show that the proposed model reduces latency, cost, andtransaction time as compared to traditional approaches. Sim-ilarly, a work that uses Ausubel’s clinching auction basedenergy trading to enhance DSM of smart grid have beencarried out by authors in [46]. The work ensured that theproposed mechanism enhances scalability in order to run allblockchain operations in an efficient manner.
3) Efficient Auction Mechanism Design:
Developingefficient auction mechanisms, which can be replaced withtraditional first price auctions is an important step towardsgreen energy auctions for blockchain. One such mechanismthat works over the phenomenon of reverse auction to increaseauction design efficiency have been presented by authorsin [44]. This work also analysed EV auction based powertrading mechanism for grid connected EVs. The proposedwork enhanced transaction matching and quick convergencein order to utilize energy in the most efficient manner.
D. Summary and Lessons Learnt
Integrating decentralized blockchain with smart grid auc-tions have paved path for future grid networks in which userscan trade their energy with full trust. However, integration ofgreen aspects in blockchain based energy auction scenariosstill require further research. For instance, the seven designrequirements that we discussed in Section III have not beenfully addressed in the works and only few works partiallyaddress these requirements. However, it is worthy to mentionthat the works involving double auction are more inclinedtowards meeting multiple design requirements. For instance, itcan be seen from Table. III that a significant number of doubleauction articles worked over enhancing energy consumptioncost in order to reduce the overall energy usage. Similarly, thesecond dominant aspect that can be found in double auctionworks is that they worked over enhancing transaction cost inorder to reduce network communication overhead. Similarly, some other articles also worked over balancing of energygeneration and consumption ratio in order to reduce the carbonfootprint from fossil fuel energy.From perspective of Vickrey auctions, only the aspect ofenergy cost reduction can be seen in the literature. One workinvolving Vickrey auction focused over usage of consortiumblockchain for efficient consensus, while the other workmanaged market surplus energy in an efficient manner viaQuasi-ideal trading. However, a work that purely addressesall design requirements of a green energy auction has notyet published from perspective of Vickrey auctions. Similarly,from perspective of conventional first price auctions, certainworks tried to provide efficient energy consumption alongsideenhancing transaction cost. Similarly, the focus of remainingof conventional first price auction works was to develop costeffective architecture and market design.To conclude, overall, a trend of enhancing energy cost canbe seen in among all three auction categories, however, thecategory of conventional first price auction dominates indesigning of efficient transaction and data storage models.Therefore, if one is interested to design an application inwhich nodes have limited memory and can handle less datavolume, then works in the category of first price auction canplay their role. Contrarily, if one’s application has nodes withgood storage power and are more energy constrained, thenworks from double and VCG auction can play their role insuch development.V. C HALLENGES AND F UTURE R ESEARCH D IRECTIONS
Development of green energy auctions for blockchain basedenergy trading also has certain challenges due to transparentand computationally complex nature of blockchain. In thissection, we discuss certain challenges, open issues, and theirpossible future research directions from the perspective ofgreen aspect integration in blockchain based energy auctions.
A. Energy Harvesting
Efficient usage of energy along with energy harvesting isone of the major design requirement that we discussed in Sec-tion III. Similarly, this aspect is also one of the most significantchallenge that green blockchain energy networks are facing.Traditional energy harvesting devices use kinetic, solar, RF,or thermal energy as a source [49]. These energy harvestingdevices are being used by IoT nodes to generate energy forcommunication and transmission [20]. However, contrary toIoT nodes, blockchain nodes require large energy to carryout communication especially at the time of consensus. Thisis because in blockchain consensus, a block goes through alot of phases such as broadcast, verification, acknowledge-ment, approval, etc. In all these phases, block needs to besent to all nodes via communication medium, which incura lot of energy . Therefore, small energy harvesting devicesare not capable to provide energy for this much extensivecommunication. Certain that carry out broadcasting via energyfrom energy harvesting devices have been carried out in thepast [50]. However, a work purely focusing over broadcastingof blockchain via energy harvesting is missing. Therefore, design and development of such energy harvesting deviceswhich are purely developed for the purpose of blockchainbased energy grid needs more attention of researchers.
B. Integration of AI in Auctions
Machine learning is being applied to auctions in order tocarry out various statistical operations, such as prediction ofthe outcome of auctions such as hammer price, or numberof successful buyers and sellers [51]. Similarly, another usecase of machine learning is to automate auction market in adecentralized way [52]. Moreover, deep learning is also beingused to predict optimal revenue of an auction mechanismhaving fixed budget [53]. Since, carrying out machine/deeplearning is a computationally complex task and certain timesone need computers with high processing power in orderto process large amount of data. Therefore, if one want toapply machine/deep learning with blockchain based auction,then he has to traverse through all blocks in order to getrequired information. Therefore, there is a need to designsuch machine/deep learning based prediction and analysismodels which use minimal resources while fetching andtraining data from blockchain decentralized ledger. Some re-searchers worked over this integration of blockchain, auction,and machine learning [54], [54]. However, this direction ofmachine/deep learning for blockchain based energy auctionshas huge potential which can be explored further.
C. Privacy Preservation in Green Blockchain based EnergyAuctions
Blockchain based energy networks do also comes up withvarious privacy issues due to their transparent nature [55].The data of transactions and trading is publicly disseminatedon ledger in order to enhance trust, but this also raisesvarious privacy concern. For instance, this data can be used byadversaries to carry out some malicious activities. Therefore,the works which consider development/integration of greenaspect in blockchain based energy trading do also needsto consider overcoming privacy issues such as transactionaland consensus privacy in order to reduce any prospectiverisk. Certain decentralized energy auction works consideredintegration of privacy preservation strategies [56]. However,this direction of private auctions require further exploration, asvery minimal work has been carried out yet. For instance, onedirection could be to preserve privacy of microgrids tradingtheir excessive energy. Another direction could be preservingthe privacy of bidding nodes which do not want to showtheir private valuations of energy trading. Similarly, optimizedprivate consensus mechanisms can also be developed whichshould focus over preserving privacy of mining nodes along-side using minimal computational cost.
D. Dynamic Spectrum Access for Green Communication
Excessive communication cost is one of the major hurdlein development of green networks [57]. Plenty of researcheshave been carried out to overcome this communication costcurse [58]. One of the significant direction is the integration of dynamic spectrum access via cognitive radio technologyin blockchain based auction networks. Certain works high-lighted the integration of cognitive radio with application ofblockchain [59]. However, a work that purely targets cog-nitive radio based auction communication for decentralizedsmart grid has not been discussed in literature. Therefore,research can be carried out in this integration of blockchainbased energy auctions with cognitive radio networks. E.g.,blockchain nodes can serve as cognitive radio nodes and cantake advantage from various functionalities of cognitive radio,such as using unlicensed spectrum at time of inactivity or usingmultiple channels to carry out auction communication, etc.Cognitive radio can be integrated with blockchain based auc-tions at various steps. However, the most significant integrationwill be to merge the functionality of cognitive radio during thedecentralized auction consensus because communication over-head during consensus constitutes a major part of blockchaincommunication. Since cognitive radio will allow blockchainusers to access unlicensed spectrum during idle times, it willsave a massive communication overhead. Similarly, blockchainbased auctions can also take the advantage of multiple channelfunctionality of cognitive radio to provide efficient commu-nication. E.g., collection of bids and asks can be done viaseparate channels to avoid any congestion in the network.Via this integration, auction, consensus, and communicationof blockchain based energy auctions can be carried out in anefficient manner. VI. C ONCLUSION
Blockchain based energy auctions is a novel paradigm inenergy trading, and it has been discussed by many researchersdue to its numerous benefits such as transparency, trust, etc.A lot of work have been carried out by researchers to en-hance to integrate blockchain with energy auctions. No doubt,blockchain based energy auctions are beneficial in many ways,but it also faces a serious challenge of communication andcomputational scarcity because of its consensus feature. As inorder to maintain a uniform blockchain state, every node hasto update its ledger in an even manner, which is usually doneby utilizing a lot of communication and computational power.Therefore, these issues give birth to another dimension namedas ‘green aspect’ in blockchain based energy trading. In thisarticle, we highlighted the need of green aspect in blockchainbased energy auctions, then we highlighted certain designrequirements which needs to be considered while developmentof such auctions. Afterwards, we analysed various technicalworks that has been carried out in this domain. Finally, wedemonstrated certain challenges and possible future researchdirections for green integration in blockchain based smart gridauctions. R
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