Helge V. Larsen

Aggregated dynamic simulation model of district heating networks

Abstract The dynamic properties of district heating (DH) networks include water flow and propagation of heat from production plants to consumers. Mathematical models of such networks can be applied, either for general understanding of DH systems, or in combination with production planning and optimization. One type of mathematical model involves a full physical modeling of the network, taking into account individual pipes, dimensions, material properties etc. Such full models tend to be computationally intensive when applied in network simulations, which can be a problem when considering large DH systems. In the current paper, a method is presented in which a fully described model of a DH network is replaced by a simplified one, with the purpose of reducing simulation time. This simplified model is generated by gradually reducing the topological complexity of the original network. The method is validated by applying it on a real case study, in which a network with over 1000 pipes is reduced to less than 10 pipes. The results show that such relatively simple networks can maintain most of the dynamic characteristics of the original networks.

Hydrogen as an energy carrier: scenarios for future use of hydrogen in the Danish energy system☆

Scenarios for a transition to a hydrogen society are constructed for Denmark. The physical basis for the scenarios is the exploitation of renewable energy resources already in progress in Denmark. Hydrogen is proposed as a convenient energy carrier due to its versatility in use, transmission and as an energy storage medium. Two main scenarios are constructed, differing in the degree of decentralisation of energy production and management: one resembles the current system with centralised facilities and commercial management, the other being based upon a projected scale-independent cost structure of energy producing and handling equipment, that will allow extreme decentralisation of the physical energy conversion system, possibly accompanied by a similar decentralisation of ownership and control. The simulation studies show that both scenarios are technically feasible, and that the storage problems arising from the mismatch between demand and intermittent sources can be solved in both a centralised and a decentralised fashion.

Probabilistic production simulation including combined heat and power plants

Expansion planning of combined heat and power systems requires simulation tools for estimating key indicators for decision making. For power systems, so-called probability production simulation techniques have been used extensively. These techniques have been extended to include combined heat and power (CHP) systems with a single heat area and back-pressure type CHP units. In this paper, existing simulation methods for CHP are extended to include extraction power plants. Furthermore, the case of multiple heat areas is addressed and three different simulation strategies are presented for such systems. The results show that an assumption of perfectly correlated heat demands in all heat areas gives results that are very similar to a general case, whereas working with a system with all heat areas aggregated into one gives rather poor results. It is demonstrated that it is possible to use the traditional concepts and methods for power-only analysis on a CHP system. Additional concepts are presented, depending on the heat criterion applied. It is concluded that probabilistic production simulation including CHP units can be performed with reasonable effort and accuracy.

Advanced Unit Commitment Strategies in the United States Eastern Interconnection

This project sought to evaluate the impacts of high wind penetrations on the U.S. Eastern Interconnection and analyze how different unit commitment strategies may affect these impacts.

A European model for the number of End-of-Life Vehicles

This paper describes a model for the projection of the number of End-of-Life Vehicles (ELVs) and presents a baseline projection. Historical data on population, the number of cars per capita (car density), GDP per capita, and the vintage distribution of cars are combined to model ELVs. The lifetime of vintages of cars is described by a Weibull distribution and the development in car density is modelled by a Gompertz function. Parameters of the distribution and function are calibrated by using historical data, mainly from Eurostat. The paper presents a baseline projection of the number of ELVs for the EU25.