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[en] Highlights: • Pb-acid and Li-ion batteries are compared under three different retail tariffs. • The battery ageing, i.e. capacity and discharge capability reduction is simulated. • A dynamic tariff (1-h resolution) increases the battery discharge value up to 28%. • A Li-ion cost of 375 CHF/kW h is required for Geneva for PV energy time-shift. • This requirement becomes 500 CHF/kW h if demand peak-shaving is also performed. - Abstract: The use of batteries in combination with PV systems in single homes is expected to become a widely applied energy storage solution. Since PV system cost is decreasing and the electricity market is constantly evolving there is marked interest in understanding the performance and economic benefits of adding battery systems to PV generation under different retail tariffs. The performance of lead-acid (PbA) and lithium-ion (Li-ion) battery systems in combination with PV generation for a single home in Switzerland is studied using a time-dependant analysis. Firstly, the economic benefits of the two battery types are analysed for three different types of tariffs, i.e. a dynamic tariff based on the wholesale market (one price per hour for every day of the year), a flat rate and time-of-use tariff with two periods. Secondly, the reduction of battery capacity and annual discharge throughout the battery lifetime are simulated for PbA and Li-ion batteries. It was found that despite the levelised value of battery systems reaches up to 28% higher values with the dynamic tariff compared to the flat rate tariff, the levelised cost increases by 94% for the dynamic tariff, resulting in lower profitability. The main reason for this is the reduction of equivalent full cycles performed with by battery systems with the dynamic tariff. Economic benefits also depend on the regulatory context and Li-ion battery systems were able to achieve internal rate of return (IRR) up to 0.8% and 4.3% in the region of Jura (Switzerland) and Germany due to higher retail electricity prices (0.25 CHF/kW h and 0.35 CHF/kW h respectively) compared to Geneva (0.22 CHF/kW h) where the maximum IRR was equal to −0.2%.
[en] Highlights: • PbA-acid and lithium-ion batteries are optimised up to a 100-home community. • A 4-period real-time pricing and Economy 7 (2-period time-of-use) are compared. • Li-ion batteries perform worse with Economy 7 for small communities and vice versa. • The community approach reduced the levelised cost by 56% compared to a single home. • Heat pumps reduced the levelised cost and increased the profitability of batteries. - Abstract: Community energy storage (CES) is becoming an attractive technological option to facilitate the use of distributed renewable energy generation, manage demand loads and decarbonise the residential sector. There is strong interest in understanding the techno-economic benefits of using CES systems, which energy storage technology is more suitable and the optimum CES size. In this study, the performance including equivalent full cycles and round trip efficiency of lead-acid (PbA) and lithium-ion (Li-ion) batteries performing demand load shifting are quantified as a function of the size of the community using simulation-based optimisation. Two different retail tariffs are compared: a time-of-use tariff (Economy 7) and a real-time-pricing tariff including four periods based on the electricity prices on the wholesale market. Additionally, the economic benefits are quantified when projected to two different years: 2020 and a hypothetical zero carbon year. The findings indicate that the optimum PbA capacity was approximately twice the optimum Li-ion capacity in the case of the real-time-pricing tariff and around 1.6 times for Economy 7 for any community size except a single home. The levelised cost followed a negative logarithmic trend while the internal rate of return followed a positive logarithmic trend as a function of the size of the community. PbA technology reduced the levelised cost down to 0.14 £/kW h when projected to the year 2020 for the retail tariff Economy 7. CES systems were sized according to the demand load and this approximated the performance of PbA and Li-ion batteries, the capital cost per unit energy storage (kW h) of the latter assumed to be the double.
[en] Highlights: • The performance and economic benefits of Pb-acid and Li-ion batteries are compared. • The business case during the decarbonisation pathway is assessed. • The aggregation from a community approach reduced the levelised cost by 37% by 2020. • For a forecast price of 16.3 p/kW h Li-ion battery cost must be less than 275 £/kW h. • A 10% subsidy will be needed for Li-ion batteries to achieve the 2020 forecast. - Abstract: A novel method has been designed to obtain the optimum community energy storage (CES) systems for end user applications. The method evaluates the optimum performance (including the round trip efficiency and annual discharge), levelised cost (LCOES), the internal rate of return and the levelised value of suitable energy storage technologies. A complimentary methodology was developed including three reference years (2012, 2020 and zero carbon year) to show the evolution of the business case during the low carbon transition. The method follows a community approach and the optimum CES system was calculated as a function of the size of the community. In this work, this method was put in practice with lead-acid (PbA) and lithium-ion battery (Li-ion) technologies when performing PV energy time-shift using real demand data from a single home to a 100-home community. The community approach reduced the LCOES down to 0.30 £/kW h and 0.11 £/kW h in 2020 and the zero carbon year respectively. These values meant a cost reduction by 37% and 66% regarding a single home. Results demonstrated that PbA batteries needs from 1.5 to 2.5 times more capacity than Li-ion chemistry to reduce the LCOES, the worst case scenario being for the smallest communities, because the more spiky demand profile required proportionately larger PbA battery capacities
[en] Electricity storage (ES) has the potential of offering several energy system benefits but different technologies also offer different services which can be traded on different markets. In this study, a combined assessment methodology is proposed, enabling a benchmark comparison of stationary electricity storage technologies for different time and system scales, considering their technical, economic and environmental performance. The results show that for short time scale (0.01 h), battery stands out with an advantage in terms of levelised costs, while Advanced Adiabatic (AA-) and Isothermal (I-) Compressed Air Energy Storage (CAES) have relatively low life cycle Greenhouse Gas (GHG) emissions. For the medium time scale (4.5 h), I-CAES shows the best performance for small scale systems, while for large scale systems, Pumped Hydro Storage (PHS) and AA-CAES show best performance. In our long time scale (seasonal) scenario, Power-to-gas-to-power (P2G2P) has lower levelised costs due to low or avoided investment for storage of gas, but higher GHG emissions than other technologies. If existing reservoirs can be utilized for PHS, it can be economically competitive to P2G2P for seasonal storage. However, storage capacity required for seasonal storage should also be taken into account, for which P2G2P has more flexibility. - Highlights: • Stationary electricity storage assessment combining techno-economic and life cycle assessment. • Current and future performance variations, type and price of electricity stored were considered. • Performances of storages were investigated under different time- and system-scales. • Storage technologies perform quite differently based on applications and the electricity stored. • Recommendations were made in terms of preference of technologies for different applications.