Scope, Methodology, and Structure: This study examines efficient and cost-effective storage options using a Smart Energy Systems Approach, showing that optimal storage solutions arise from integrating sub-sectors of the energy system. It synthesizes the authors' prior research, analyzing storage in different energy system segments, storage size, cost, and thermal storage's role. The study also considers cooling, transportation, and biomass integration, demonstrating the benefits of a smart energy systems approach incorporating efficient storage utilization. Electric, Thermal, Gas, and Liquid Energy Storage: There is a fundamental cost distinction between storing electricity and other forms of energy. Electricity storage is storage where inputs and outputs are primarily electricity, though it often involves converting electricity into other energy forms. This conversion process makes electricity storage more expensive than storing thermal energy, gas, or liquid fuels. For instance, thermal storage is approximately 100
times more economical than electricity storage, and gas and liquid fuel storage technologies have even lower investment requirements. These comparisons are based on technologies like underground natural gas caverns and oil tanks. Still, future renewable energy systems could also use methane or methanol from biomass and hydrogen from electrolysis. Beyond investment costs, electricity storage also faces higher losses, especially in conversion. Gas caverns and oil tanks exhibit negligible losses, while thermal storage has about 5% losses, depending on size and retention time. Since electricity storage involves conversion to and from storage, these losses are more substantial. Due to these high investment costs and losses, the economic viability of electricity storage technologies is highly dependent on electricity price variations, which typically occur daily. However, the intermittent nature of renewable electricity sources like wind power tends not to generate significant price variations, making investments in electricity storage economically unfeasible in high-wind power systems like
Price Cycle efficiency
1.000.000
0 10 20 30 40 50 60 70 80 90 100
Figure 1: Investment cost and
100.000
cycle efficiency comparison of
electricity, thermal, gas and liquid fuel storage technologies. See assumptions, details and references in Appendix 1.
10.000
1.000
100
10
1
Electricity - PHS
Thermal
Gas cavern
Liquid Fuel
40
Figure 2: Annualized
35
investment cost per use-cycle vs annual numbers of use-cycles. In the diagram the cost is also benchmarked against the cost of producing renewable energy, here shown for a wide cost span by grey (extension along horizontal axis is for presentation only; there is no cyclic dependence for renewable energy production).
30
25
20
15
10
5
0
0
50
100
150
200
250
300
350
400
Number of cycles per year
Thermal
Electricity
Gas
Liquid
RES production
5
www.dbdh.dk
Made with FlippingBook - Online magazine maker