How much cheaper must a store's electricity be than a heat pump's for a sand heat store to deliver heat for less?
research/energy-thermal-cost
How much cheaper must electricity be for a sand heat store to beat a heat pump? Sourced costs (PyPSA technology-data) on the energy-thermal model: a daily-cycled store needs the pump's electricity about 2 times dearer, weekly 5, monthly 16, seasonal 120 (house); the heat lost in standby, not the sand, rules out seasonal storage.
What it found
Costs the sand store of energy-thermal with every capital cost, lifetime, O&M and efficiency read from PyPSA technology-data (Danish Energy Agency; Viswanathan et al. 2022, PNNL-33283) at pinned revisions, sizing it with the transient model and comparing levelised cost of heat against an air-source heat pump. A sand store charged at EUR 0.05/kWh beats a heat pump when the pump's electricity costs about 2 times as much if the store cycles daily, 5 times weekly, 16 times monthly and 120 times seasonally (house, 10 MWh a year; 222 m3 and EUR 1.53 of capital per kWh for the seasonal store); at district size (5 GWh a year) 2.2, 2.8, 5.3 and 38 times. At 3 times the store can stand 2 days (house) or 7 (district); at 10 times, 14 or 60. A district hot-water tank beats sand for monthly and seasonal storage. Not from a source: electricity prices (swept), 2,000 full-load hours, 0.5 m insulation, cycle counts. Limitations: the sand-store cost is a utility-scale figure, no heat exchanger is costed (favours the store), flat prices, constant COP, instant discharge.
A figure from its own output
Paper, code and results
More in Energy supply and dense energy storage
- If a sand heat store buys electricity only in the cheap hours of a German price series, when does it beat a heat pump?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.
- On real German day-ahead prices, does a sand heat store beat a heat pump, and was the modelled price right?On real German day-ahead prices, does a sand heat store beat a heat pump? Yes at wholesale: daily cycling wins in all 5 years (EUR 0.045–0.062/kWh against 0.070–0.074) and weekly in 4; the earlier merit-order model was flat at EUR 54.6/MWh and wrong; a EUR 0.10/kWh levy removes the win.
- How much is a home battery worth on a time-of-use tariff if it is dispatched optimally?How much is a home battery worth on a time-of-use tariff with optimal dispatch? An LP breaks even at $867/kWh for 10 kWh behind 6 kW PV, against $674 for the best fixed rule ($742 with a 4,000-cycle life); a rolling 36 h plan matches the year optimum (
energy-touwith an optimiser). - How much of an optimal home-battery controller's gain survives a realistic forecast?How much of an optimal home-battery controller's gain survives a realistic forecast? With yesterday's weather or a 7-day mean as the forecast, a rolling LP saves $726 or $691 a year against the fixed rule's $694 (perfect forecast: $892); 84–101% of the gain is lost (
energy-tou-lpwith forecasts). - How much of the home-battery optimiser's forecast loss does re-planning every few hours recover?How much of the home-battery optimiser's forecast loss does re-planning every few hours recover? On PVGIS typical-year data for three US sites, re-planning the LP every 3–12 h instead of daily adds $10–36 a year and closes at most 17 points of the gap to a perfect forecast (10 kWh, assumed tariff);
energy-tou-lp-tmywith receding-horizon re-planning. - Does a clear-sky-index forecast rescue the optimal home-battery controller on real weather?Does a clear-sky-index forecast rescue the optimal home-battery controller on real weather? On PVGIS typical-year data for three US sites, a rolling LP fed yesterday's weather or a clear-sky-index forecast keeps 25–55% of the perfect-forecast gain over the fixed rule at Phoenix and Seattle and none of it at Golden (10 kWh, assumed tariff);
energy-tou-lp-forecaston measured-derived irradiance.
All 39 Energy supply and dense energy storage projects →
Other research topics
Proper scoring & elicitation28Effort & peer prediction9Verification games & slashing19Detection & tolerances14Markets as routers13Prediction-market design9Paying contributors8Decentralised training systems23Digital twins & sim-to-real164LLM chip design loops40Robot manufacturing loops53Ambient AI assistant46Self-replicating manufacturing34Simulation-first design64Engineered clothing45Task-specific AI accelerators40Algorithmic chip-design loops42Open-source purpose-built robots44The software-engineering loop43Adversarial human imitation41Open-source residential construction41Autonomous multi-angle capture34Sensing, imaging and 3D31Energy supply and dense energy storage39Robot societies among people31Agentic co-design of low-cost robots27Laundry-hanging robots25Machine learning on qualitative data23Robots on the building site27Civilizations & group psychology1History & human sciences1
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.