Abstract
Sorption thermal energy storage (STES) has the potential to have higher energy densities and lower thermal losses compared to conventional thermal storage technologies, and it can contribute to increase the energy grid flexibility and the penetration of intermittent and distributed energy sources. However, STES is a technology still under research, and system-scale investigations are necessary to determine its potential in future energy systems. In this regard, the objective of this work is to investigate the STES potential in a reference energy system interacting with different energy markets. The system consists of a geothermal doublet supplying thermal energy to an organic Rankine cycle (ORC) and to a district heating network that satisfies the thermal energy demand of a residential neighborhood. A techno-economic optimization of the energy system is carried out using mixed integer linear programming. The optimization aims at finding the optimal STES size and system operational behavior that maximizes the yearly profits from selling the ORC energy to the energy markets. Among the main results, it is found that the STES integration increased the overall system profits by 41% in the scenario where the ORC interacted with the UK day ahead market (2017 data), and with two UK balancing services: the capacity market, and the short term operating reserve. In conclusion, this work highlights how a thermal storage technology still under research could become an asset under specific market conditions. Future policy mechanisms can benefit from similar analyses and foster the integration of new technologies into the energy grid.
Highlights
The increasing energy requirements of human society [1] and anthropogenic global warming [2] are among the main drivers for a transition towards sustainable energy systems, based on renewable energy sources such as solar and wind, in which anthropogenic CO2 emissions are reduced [3]
The reason is that the storage integration, even with the smallest investigated size, would have resulted in Sorption thermal energy storage (STES) CAPEX and OPEX higher than the additional revenues stream generated by the organic Rankine cycle (ORC) thanks to the STES presence
The integration of a sorption thermal energy storage (STES) in an energy system operating in different energy markets has been investigated
Summary
The increasing energy requirements of human society [1] and anthropogenic global warming [2] are among the main drivers for a transition towards sustainable energy systems, based on renewable energy sources such as solar and wind, in which anthropogenic CO2 emissions are reduced [3]. The fluctuating nature of solar and wind will require a higher degree of flexibility, in which energy production and usage can be spatially and temporarily decoupled. In this regard, thermal energy storage can be beneficial as thermal energy accounts for most of the final energy use in European households [4] and industry [5]. CAPEX CM DAM DHN HG HR HX LCOS MILP OPEX ORC STES STOR capital expenditure capacity market day ahead market district Heating Network main heating grid heat recovery unit heat exchanger levelized cost of storage mixed integer linear programming operating expense organic Rankine cycle sorption thermal energy storage short term operating reserve market. The integration of seasonal heat storage at district level has been investigated for increasing the amount of renewable heat supply [14]
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