• Energy Research

Abstract In central Europe, the number of photovoltaic battery storage systems is steadily growing. Combined with a heat pump for power-to-heat coupling, these storage systems can contribute to sector coupling and increase the use of renewable energies in private households. The growing share of renewable energies leads to further fluctuations in the grid and a growing demand for reserve power. Integrated homes that combine a photovoltaic battery storage system with power-to-heat coupling can contribute to providing control reserve. The frequency restoration reserve in central Europe is divided into a negative and a positive reserve market, enabling market opportunities for integrated homes. Integrated homes participating in the negative frequency restoration reserve market could benefit from energy at low costs. Therefore, integrated homes profit from the additional flexibility provided by the heating sector. Low-cost energy from dual-use operation could lead to enhanced economics of integrated homes, especially during the winter. This paper presents the calculation of the marginal costs and savings for the market participation and the resulting economic influence on integrated homes. Costs for additional battery aging, as well as savings for reduced domestic energy consumption from the grid and an enhanced feed-in, are taken into account. The results show that participation in the German frequency restoration reserve market could reduce the annual costs for heat and electricity of integrated homes by up to 14.5%. A dual-use operation could be beneficial for integrated homes and enhance their market penetration.

Abstract The number of households with photovoltaic battery storage systems is steadily growing, and so is the number of heat pump installations. An integrated home combines domestic battery systems and a heat pump for power-to-heat coupling. During winter, storage systems in an integrated home are not used to their full capacity due to low solar radiation. This potential can be used to enhance the economics by applying a dual-use scheme. In this publication, an integrated home that participates in the frequency control reserve market is investigated. A major advantage of integrated homes with power-to-heat coupling in comparison to standalone battery storages is the additional flexibility to absorb negative control reserve power in the heating sector. Seasonal variation of feed-in from photovoltaics is considered by an advanced strategy for variable provision of control reserve. Results show that a dual-use operation with participation in the control reserve market can increase the profitability of storage systems. Market participation leads to accelerated battery aging, mainly driven by increased calendar aging. This is overcompensated by the possible incomes. Under consideration of low costs for market participation, a constant provision of at least 3 kW of reserve power could be economical. A variable provision further enhances economic efficiency.

10th International Renewable Energy Storage Conference, IRES 2016, 15-17 March 2016, Düsseldorf, Germany / Edited by Peter Droege 10th International Renewable Energy Storage Conference, IRES 2016, Düsseldorf, Germany, 15 Mar 2016 - 17 Mar 2016; Amsterdam [u.a.] : Elsevier, Energy procedia, 99, 80-88 (2016). doi:10.1016/j.egypro.2016.10.100 Published by Elsevier, Amsterdam [u.a.]

Abstract Photovoltaic battery energy storage systems can increase the self-consumption from residential PV systems and therefore contribute to a decentralized renewable electricity system. Rising electricity prices and decreasing battery prices enhance the economics of residential battery storage. Intelligent operation strategies could further improve the economics and lead to grid relief as well. This paper presents new forecast-based operation strategies for increased battery lifetime and reduced curtailment of PV power feed-into enhance system economics. In addition, these strategies are compared to different commonly used operation strategies in terms of economics and self-sufficiency of the system. Increased battery lifetime is achieved by reducing the average state of charge of the battery by limiting the stored energy according to the predicted energy demand during night. Forecast-based operation strategies are used in combination with variable power feed-in limits of the PV battery storage system to relieve the grid. Two different forecast strategies are discussed: the perfect forecast, which is used as the best case, and the persistence forecast, representing the worst case in terms of forecast accuracy. The operation strategies are evaluated by simulating a DC-coupled PV and battery system. The model is parameterized with measured data from cell testing and battery aging tests. The levelized cost of electricity is used for the economic evaluation of the operation strategies. Results show that the developed forecast-based operation strategy can drastically increase battery lifetime and thus total energy throughput and therefore reduce the levelized cost of electricity by up to 12%. This has been shown effectively for two different types of battery cell, a low-cost consumer cell and a high-quality battery cell. The combination of forecast-based operation strategies with variable feed-in limits can nearly eliminate curtailed PV energy for the simulated system. Sensitivity analyses of component sizing and load profile confirm the findings. The developed strategy can easily be implemented on real residential PV battery energy storage systems since no additional communication interface is required.

Journal of energy storage 29, 101153 (2020). doi:10.1016/j.est.2019.101153 Published by Elsevier, Amsterdam [u.a.]

Renewable energies from residential photovoltaic systems can be used in the electricity sector as well as in the residential heating sector. Therefore, sector coupling, for example by using heat pump systems, is mandatory. Integrated homes use photovoltaic energy for space heating and domestic hot water to contribute to the decarbonization of the heating sector. The economics are a key to increasing the market penetration of integrated homes. Combined operation strategies for the electricity sector as well as for the heating sector can enhance the economics of these systems. This paper analyses different operation strategies for both electrical and thermal systems and examines the gain in efficiency by combined strategies. Furthermore, the dimensioning of the different system components heavily influences the economics of the integrated home. Capital-intensive components, such as photovoltaic generators, battery storage systems, heat pumps, and thermal storage units, play a major role for the profitability. Therefore, the optimization of component sizing is necessary in order to enhance the economics of the system. This paper presents optimization results based on the covariance matrix adaptation evolution strategy. The results of the paper indicate that combined operation strategies as well as the optimization of the component sizes strongly influence the economics of photovoltaic battery energy storage systems with power-to-heat coupling. The impact of the optimization on the economic efficiency is higher compared to the influence of advanced combined operation strategies. The optimization indicates that relatively small storage units are more economical. The use of the heating sector as additional storage for excess photovoltaic energy is only economical to a minor degree, because it reduces the coefficient of performance of the heat pump. Keywords: Photovoltaics, Battery energy storage systems, Power-to-heat coupling, Integrated homes, Optimization

Abstract The number of PV battery energy storage systems (PV BESS) as well as the number of heat pumps in domestic households in Germany is continuously increasing. Heat pumps enable the use of electricity for both electrical and thermal appliances. Therefore, they can play a major role to enhance the decarbonisation of the heat sector. Heat pumps are operated in combination with a thermal storage in order to reduce the switching cycles of the heat pump. A combination of a heat pump system and a PV BESS could enhance the flexibility of such a system. The flexibility of the battery storage is combined with the flexibility of the heating system by the thermal storage capacity of the building itself and the thermal storage unit of the heat pump. Numerous operation strategies for PV BESS as well as for heat pump systems already exist. The combination of these two systems demands for intelligent operation strategies that use the flexibility of both components and could enhance the overall energy efficiency within the household. This paper analyses the different operation strategies for both electrical and thermal storage systems and examines the gain in efficiency by combined strategies. Operation strategies that enhance battery lifetime of a PV BESS are extended to efficiently fulfil the demand of the heat system additionally. The influence of the operation strategies is investigated by the use of the levelized costs of energy (LCOEnergy). Additionally, the levelized costs of heat (LCOH), as well as the levelized costs of electricity (LCOEle), are calculated to compare the investigated system with conventional electricity and heat systems. The results show that PV BESS with power-to-heat applications enhance the self-consumption and the self-sufficiency rate. Prognosis based operation strategies are suitable to meet the requirements of both systems. Last but not least the results indicate that domestic power to heat (P2H) systems are economically competitive with fossil heating systems.

10th International Renewable Energy Storage Conference, IRES 2016, 15-17 March 2016, Düsseldorf, Germany / Edited by Peter Droege 10th International Renewable Energy Storage Conference, IRES 2016, Düsseldorf, Germany, 15 Mar 2016 - 17 Mar 2016; Amsterdam [u.a.] : Elsevier, Energy procedia, 99, 174-181 (2016). doi:10.1016/j.egypro.2016.10.108 Published by Elsevier, Amsterdam [u.a.]