Gerardus Johannes Maria Smit

Demand side management using profile steering

Many Demand Side Management (DSM) approaches use energy prices as steering signals. This paper shows that such steering signals may result in power quality problems and high losses. As an alternative, this paper proposes to use desired (e.g., flat) power profiles as steering signals and presents an efficient scheduling algorithm that can follow desired power profiles. This paper investigates the complexity of price and profile steering, and presents an algorithm for profile steering. The evaluation of this algorithm studies the results of a best possible uniform pricing and profile steering for a case of 121 houses, each with an electrical vehicle of which the power consumption can be controlled and shifted in time. In contrast to the other evaluated approaches, our profile steering algorithm results in a much flatter profile and keeps the voltage between 220V and 235V at each node. It reduces distribution losses by 57% compared to no control, and by 48% compared to uniform pricing.

Generation of flexible domestic load profiles to evaluate Demand Side Management approaches

Various Demand Side Management (DSM) approaches have been developed the last couple of years to avoid costly grid upgrades. However, evaluation of these DSM methodologies is usually restricted to a use-case specific example, making comparison between different DSM approaches hard. This paper presents a novel, open source, load profile generator to evaluate and compare DSM approaches. In addition to static load profiles for both active and reactive power, it also provides flexibility information for various classes of controllable domestic devices. Load profiles and flexibility information are generated using a simple behavioural simulation. The output data uses 1 minute intervals and incorporates device measurements. The generated profiles are in sound with the measurement data obtained in a field test on both the household level and aggregated neighbourhood level. The same dynamics, such as unbalanced loading and rapid power consumption fluctuations, are observed in the generated model.

House thermal model parameter estimation method for Model Predictive Control applications

In this paper we investigate thermal network models with different model orders applied to various Dutch low-energy house types with high and low interior thermal mass and containing floor heating. Parameter estimations are performed by using data from TRNSYS simulations. The paper discusses results in relation to model order and the order which yields a sufficient level of accuracy is determined. The paper presents a semi-physical estimation method which is used to improve correlation of model parameters with physical determined values. The thermal network model can be used for various simulation studies or for Model Predictive Control (MPC) of house heating or cooling systems. The paper investigates accuracy of the model for MPC by comparing MPC-results with results from TRNSYS simulations, including ventilation heat losses.

Soft-islanding a group of houses through scheduling of CHP, PV and storage

In this paper we investigate the possibility of soft-islanding (near-autonomous operation) a group of houses from the electric power grid in the Netherlands. Energy balancing is possible through applying multi-mode smart grid scheduling for controllable energy generation, storage and consumption devices. The modeled neighborhood consists of modern, well-insulated terraced houses in a typical Dutch climate, each equipped with roof-mounted photovoltaic (PV) panels. The panels are sized to cover the daily electric demand during sunnier parts of the year where the heat demand is low. The system also includes a centrally placed combined heat and power (CHP) with hot water and electric storage, and controllable devices within the houses such as washing and dishwashing machines. The daily domestic hot water demand is supplied entirely by the central CHP. The investigation includes an estimation of system dimensions, e.g. PV, CHP and storage capacities based on daily supply and load profiles on top of the multi-level scheduling. Through simulations we demonstrate the technical feasibility for off-grid operation of this neighborhood.

Digitally assisted analog beamforming for millimeter-wave communication

This paper addresses the research question on how digital beamsteering algorithms can be combined with analog beamforming in the context of millimeter-wave communication for next generation (5G) cellular systems. Key is the use of coarse quantisation of the individual antenna signals next to the analog beamforming. The extreme case of single bit quantization is analyzed. Direction-of-Arrival (DoA) estimation, being the crucial element in beamsteering, is only slightly deteriorated compared to DoA estimation based on full precision (analog) signals. For Signal-to-Noise Ratios (SNRs) below 0 dB, single bit quantization introduces ~2 dB noise level increase. For SNRs beyond 0 dB, the standard deviation of the DoA estimate, levels out to below 10-4 radian in our specific case study. An additional correction called the Van Vleck correction, mitigates the effects of single bit quantization. This effect can clearly be seen in case multiple signals impinge on the array. When using this correction, the probability of correct detection of multiple sources (in this paper we use 2 sources) is comparable to the performance of an analog system. We therefore conclude that digital beamsteering can effectively and efficiently be combined with analog beamforming.

Considering grid limitations in profile steering

Demand side management is often envisioned as a promising technique to reduce peak loads, and match local generation and consumption in the future smart grid. To exploit flexibility offered by smart appliances, a methodology is required to steer the appliances towards better utilization of the grid. As conventional grid reinforcements are very costly, the main objective is often peak shaving to reduce stress on network assets. In this work, we consider a demand side management methodology based on profile steering. This approach generates schedules for controllable devices in a hierarchical way. We show that, when the available flexibility is unevenly distributed, profile steering leads to schedules that violate local grid constraints. We then introduce a modification that enables the methodology to consider local limits on the generated schedules. With this modification, we show that the generated schedules respect the local limits imposed without significantly altering the resulting total load profile.

Planning based real-time control using DEMKit

There is a trend towards local energy markets in order to integrate renewable energy sources and controllable devices into the energy system. As a result the market size is getting smaller and making an accurate day-ahead planning as base for acting on these markets is getting harder. As a consequence, deviations from the offered planning are more likely to occur. In this paper, we propose a planning-based real-time control method to deal with such deviations on device level in order to follow the submitted planning as good as possible. The proposed method controls the devices in each house sequentially, ordered by their flexibility (from least flexible to most flexible) and aims to realize the planned profile as good as possible without deviating too much from the individual planning for the devices.

A Practical Approach in Glycerol Oxidation for the Development of A Glycerol Fuel Cell

The research on electrochemical carbon molecule oxidation started in the past years as new electrochemistries were researched for new fuel cells systems and batteries that may line up as backup energy supply and storage systems in off-grid and on-grid microgrids, as modeled by our group at the University of Twente [1-3]. By lining up these two disciplines we hope to support the bridge between new electrochemical systems on one side, (pilot) production with partner companies, prediction, and validation of systems upon implementation in microgrids by our group. The electrochemical oxidation of glycerol in alkaline aqueous solution has been studied on gold and gold coated metals (Zn-Au and Cu-Au) by voltammetry and EIS (Electrochemical impedance spectroscopy) for possible use in a new fuel cell as an outlet for the excess glycerol that is produced in the biodiesel industry. The observations show that the gold surface may change upon cycling by cyclic voltammetry. Besides, the current density shows non-linear behavior with the square root of the scan rate, implying that the reaction is not totally controlled by diffusion. EIS analysis using the EQUIVCRT software revealed that one out of twenty tested equivalent circuits fitted the data well at potentials of -0.05 V,- 0.15 V and -0.25 V vs. Ag/AgCl, identifying resistors and a Warburg element in parallel with the double layer capacitance, the elements are possibly related to the presence of double layers associated with hydroxypyrovate and oxalate ions. The results are consistent with the low-frequency error fitting analysis (10-4), AC Simulink-Matlab fitting responds and the Kronig-Kramers transform test. The tested Zn-Au and Cu-Au electrodes show similar voltammetry behavior as the gold electrode, as witnessed by the results of cycle analysis and the scan rate analysis. The discharge chronoamperometry test further shows that the Zn-Au electrode and Cu-Au have higher current densities than the gold electrode at a potential of -0.25 V vs. Ag/AgCl (5 mA cm-2, 4.5 mA cm-2, and 3 mA cm-2 respectively).

Balancing islanded residential microgrids using demand side management

Now that the internet of things is emerging, control of domestic assets within smart microgrids is also gaining more interest. Various demand side management approaches are presented in literature to control these assets and steer the aggregated consumption profile towards a target profile. Furthermore, these microgrids may operate in islanded mode for short periods in which energy balance is important. This paper proposes a fast control method to control domestic assets in an islanded microgrid by means of 2-way communication and local measurement data. By using the potential of domestic assets, required capacity of backup storage and power ratings of backup generators can be decreased and/or the operation time of the islanded microgrid can be increased. Simulations of a use case show that the storage capacity can be significantly decreased (from 54.3 kWh to 29.6 kWh without loss of QoS) when households in a neighborhood are cooperating.

Asymmetric Shaped-Pattern Synthesis for Planar Antenna Arrays

A procedure to synthesize asymmetrically shaped beam patterns is developed for planar antenna arrays. As it is based on the quasi-analytical method of collapsed distributions, the main advantage of this procedure is the ability to realize a shaped (null-free) region with very low ripple. Smooth and asymmetrically shaped regions can be used for Direction-of-Arrival estimation and subsequently for efficient tracking with a single output (fully analog) beamformer.