If a sand heat store buys electricity only in the cheap hours of a German price series, when does it beat a heat pump?
research/energy-thermal-hourly
When does a sand heat store beat a heat pump on hourly prices? With 189 GW solar and 137 GW wind and a modelled German price series, a daily or weekly store wins in all 5 years (EUR 0.027/kWh against 0.071); a levy of 0.10/kWh or a surplus-hour price above about 20–35 EUR/MWh removes the win.
What it found
Replaces the flat electricity price of energy-thermal-cost with a modelled hourly price built from real German hourly load, solar and wind (OPSD/ENTSO-E, 2015–2019) and a one-fuel merit order (gas at EUR 54.6/MWh from PyPSA technology-data; surplus hours at a floor of 0, swept to 40). The store buys the cheapest quarter of each cycle; the heat pump pays the November–March mean. With the 189 GW solar and 137 GW wind of the 80%-emissions-cut optimum of energy-mix-sourced, a house-sized sand store cycled daily or weekly beats the pump in all five years (EUR 0.027 and 0.032 against 0.071 per kWh of heat in 2019); monthly and seasonal storage lose. With a fleet like today's there are no surplus hours and the store loses; a levy of EUR 0.10/kWh on both prices makes it lose in every case; a surplus-hour price above about EUR 20–35/MWh ends the advantage. Not from a source: the surplus-hour floor (swept), no storage or grid in the price model, flat winter heat demand, the quarter-cycle charge window. The price is modelled, not a market price, and no taxes or network charges are included in the base case.
A figure from its own output
Paper, code and results
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Produced with AI assistance (Claude). Results are from the code in this repository and are simulated or stylised unless the abstract says otherwise; nothing here implies affiliation with or endorsement by any lab, researcher or company cited. MIT licensed.