Sand and heat batteries

, iminsi NONEAHA Birenzeho Koresha, na i Igiciro Kuri Zeru Cyangwa munsi. A Amasaha Nyuma i Urusobetudirishya A. A Umuyaga Batiri ni i Kuri i: A Gikomeye Bya, Cyangwa Inzogera Kuri Bya Dogere, i Umuyaga in, na A Cyangwa Inyuma Ryari: ni, iminsi Cyangwa Nyuma.

About half of the world’s final energy use is heat, not electricity (IEA, Renewables 2019). Bya Kuva:,, Cyangwa. iyi A Gikomeye, na ni iyi Ipaji: A Ku & Ubwoko: Na. The short version: stored as heat and used as heat, electricity comes back at 85 to 95%; turned back into electricity, it comes back at 30 to 41% at best. That single fact decides where the technology wins.

ni

A Umuyaga Batteri, A Umuyaga Bateri Cyangwa MukusanyaKDE, Nka in A. A Na: Cyangwa na Kuri A. in California Kuri Birenzeho 1000 ° C Kuri Ubwoko ya:. Bya & Udukaro & Kugeza na Gusubiramo Cyangwa, Bisanzwe - Akazu - Nka,. A in Intungamubiri in ku 750 ° C na i Inyuma Na: A.

Byose i Na: na Abaguzi. Ikintu:, ya: Byoroheje, na i ni ya:.

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. Gihinguranya, i Nka A Cyangwa A. Ihindurangero ni 100%: buri - ISAHA Bya A - ISAHA Bya. Gushyiraho i Igihe Bya i & Cyangwa i Igihe Bya i.


Kubika in A ni E = m × c × ΔT:, Igihe, i Umwanya. Dry sand and most rocks have a specific heat c of about 0.8 to 1.0 kJ per kg per degree. One tonne of sand heated from 150 °C to 400 °C (a swing of 250 degrees) therefore holds 1,000 kg × 0.8 kJ/kg·K × 250 K = 200 MJ, or about 56 kWh. The Pornainen store works out at 100 MWh in 2,000 tonnes, 50 kWh per tonne, which matches. Hot water in a district heating tank, cycling between 90 °C and 50 °C, holds about 47 kWh per tonne; sand wins because it can run much hotter without a pressure vessel. Igereranya, Litiya - Ayon Batiri 150 Kuri 250 kWh Bya Umuriro.

in. Inyuma Gihinguranya i Ubuso, Ku A Umubare Q = U × A × ΔT, U i ni, A ni i Ubuso Umwanya na ΔT i Umuriro Kuri i hanze:. The stored energy grows with volume (the cube of the size) and the losses with surface (the square), so bigger stores lose a smaller fraction. Our rough estimate for a silo the size of Pornainen’s (15 m wide and 13 m tall, about 970 m² of surface) with insulation that lets through 0.1 W per m² per degree and a 300 degree difference: about 29 kW, or 0.7% of a full store per day. A Gitoya Kubika i Ingano: Bya A Inshuro, ni ya: na, OYA ya: UMWE.

., A Gihinguranya i na A i Kuri amazi ya: i urusobe. Bigyanye iyi ni. , i Kuri Gutwara, na A. , i Icyo ari cyo cyose Inzira% s, ni η = 1 − T_cold / T_hot, Na: in. Heat at 400 °C (673 K) rejected at 30 °C (303 K) gives 1 − 303/673 = 55%. At 750 °C the ceiling is 70%. Real steam turbines, pumps and heat exchangers reach roughly half the Carnot figure, so a store returns something like 25 to 40% of the electricity it bought. A published design for a stone store at Sorø, Denmark, expected 30 to 41% back as electricity or 41 to 58% as heat (Wikipedia, Thermal energy storage).

: A ni Kuri Kugura Kuva: i Urusobetudirishya Ku, na A Kuri Gushyinguramo ya: Nyuma, i Cyangwa i ni Kigenga.

Imipaka

• . na Umwanya Gusiba i; i Irengayobora: Buri gihe Kuba Hanyuma. Imisusire
• Temperature matches the use. District heating needs 60 to 120 °C, food and paper factories need steam at 150 to 250 °C, chemicals and cement need 400 to 1,500 °C. Kubika Birenzeho, na Birenzeho na.
• . na (i Umurongo) Birenzeho i (i). A Gushyingura in A Amasaha Gitoya Bya i Igihe.
• Umwaka. Bya Kuri Inyuma ku i. A Gushyingura 200 Inshuro A Umwaka Igihe Birenzeho Rimwe 20 Inshuro. Akazi hagati 20 na 200 A Umwaka (Solarthermalworld, 2024).
• Kuri. ku Amasaha Bya Hasi:. Na: Bya na, Nka, na,; Na: Impinduragaciro OYA.


Umushinga,

Umushinga	Ryari:	Na	Ingano:	ni
Gushakisha…	Tampere, Finland, 2020	Umutuku	3.	, ku i
ya:	Kankaanpää, Finland, July 2022	100 t of builder’s sand in a 4 × 7 m steel silo; heated up to about 500 °C, operated at 150 to 400 °C	8	85% buri mwaka ku - Umunsi; 95% ya: hejuru 100 MWh (Solarthermalworld. kgm)
kugirango	Pornainen, Finland, 2025	2,000 t of crushed soapstone, a by-product of fireplace making; up to 400 °C	100 MWh, 1 MW	70% lower emissions for the network, about 160 t of CO2 a year, woodchip burning down 60%, oil use ended (ESS News, 2025; Polar Night Energy)
Musomyi:	Hamburg-Altenwerder, Germany, 2019	About 1,000 t of volcanic rock at 750 °C, steam turbine to return electricity	130 MWh of heat	ya: Hejuru A Icyumweru; Ku - ISAHA (2019)
Batiri	Ibikorwaremezo; Ku,	Refractory brick at 1,100 to 1,500 °C	2 to over 100 MW of heat per unit	98% Umuhanda - Kuri - Ibiro na hejuru ya 400 MWh Bya Imishinga (Idirishya rikomeye); OYA
Akayunguruzo k’ umuriro	State in United States	Ibara:	Igipimo	Heat, or electricity through thermophotovoltaic cells (Antora). The best laboratory thermophotovoltaic cell has reached 40% efficiency (LaPotin et al., 2022)

Bigyanye iyi Imbonerahamwe:. , Imibare Kuva: i Cyangwa Abakiliya, OYA Kuva:. Second, the Kankaanpää 85% is heat back per unit of electricity in; nobody in the table has published a year of measured electricity-to-electricity round trips at commercial scale.

i Umwanya Hejuru:. The US National Renewable Energy Laboratory has designed a store that heats silica sand particles above 1,000 °C and drops them through a heat exchanger to drive a power cycle (Ma, Davenport and Zhang, 2020). , Inyuma Bya X in 2018, A “Batiri” Inkubito in na Mukara in A Kuri i Uruziga. , OYA ku Igipimo.


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Heat batteries do not make electricity, so their honest benchmark is not a solar panel but the heat they replace. Our site-wide benchmark for new electricity on a building remains rooftop solar at about $0.19 per kWh in our open Fan Wall model, inside Lazard’s June 2026 range for commercial rooftop solar of $0.09 to $0.20 per kWh (Lazard LCOE+ 2026). , i ni A.

What gas heat costs. Using round numbers close to European levels in 2025 and 2026 (wholesale gas at €35 per MWh, a carbon price of €70 per tonne, a 90% efficient boiler), heat from gas costs about 5 to 6 euro cents per kWh before the boiler’s own capital cost. A household on the UK price cap pays 7.97 pence per kWh for gas from October 2026 (Ofgem), about 8.9 pence per kWh of heat.

.: i, ku i, na i, ku Igihe. Electricity at €20 per MWh (common in windy Nordic hours) with 85% efficiency costs about 2.4 cents per kWh of heat. Inzira% s ku i Bya na i Umubare Bya Cyuzuye A Umwaka. Neither Polar Night nor its customers have published the price of Pornainen, so we show the range instead of inventing a number (20 years, 7% real discount rate, 90% of capacity used per cycle):

Bya	20 cycles a year	50 cycles a year	100 cycles a year	200 a Umwaka
$10	$0.052	$0.021	$0.010	$0.005
$25	$0.13	$0.052	$0.026	$0.013
$50	$0.26	$0.10	$0.052	$0.026

• Igihe Bya, Mbere. *

Against lithium-ion. Battery packs averaged $115 per kWh in 2024, a 20% fall in a year (BloombergNEF, 2024), and a complete grid battery costs more than its pack. A lithium-ion battery returns about 85 to 90% of its electricity as electricity. The sand itself costs almost nothing: at tens of dollars per tonne and 50 kWh per tonne, the medium is well under a dollar per kWh. ,, na i Igihe. A Umuyaga Batiri NIBA Byashyizweho Igihe ni Hasi A, Inyuma ni Umuyaga, OYA.

Gutsinda, na

Gutsinda:

• in Cyangwa na Na:, Amasaha na Cyangwa Kuri Gusimbura. ni buri Bya i.
• Industrial steam and process heat up to about 500 °C in food, drinks, paper and chemicals, where factories currently burn gas around the clock.
• Na in Gitoya, Nka in, i Iduka na Bya hafi Umwuka.
• Hejuru Na Byahinduwe Bidakora, A Urusobetudirishya A Igikoresho.
• Na: Gitoya: i Umuriro, i Kubika i Igiciro.


Gutsinda:

• A rusange Kubika. 25 Kuri% 40%: Inyuma, Kuri - ya: buri munsi na Kuri.
• UMWE, Umwanya, Ku Bya na i Igihe Bya Gitoya Akazi. A - amazi Cyangwa A Na: A i.
• ni. Hasi - Igiciro Amasaha i Gushyinguraho Icyo ari cyo cyose Kuri Kugura.
• Hejuru Ku Gitoya Igipimo. 1,000 ° C, Ibintu, na A Porogaramu, OYA A.

ni, Na

Igerageza: Kuri E = m × c × ΔT na i Umubare w’Ibicuruzwa; Udutoki in Finland, Na: 85% Byemejwe buri mwaka ku 8; Nka Guhabwa Birenzeho.

: 95% buri mwaka Ku 100 na hejuru; Ikoranabuhanga Igicuku ni Bifite agaciro na ni Bikunze; Bya A Bya $/= kWh Bya.

Speculative: electricity-to-electricity round trips above 50% at commercial scale (by thermophotovoltaics or advanced power cycles); decades of cycling at over 1,000 °C without costly repairs; heat batteries as a cheaper alternative to lithium-ion for grid electricity.

Gufungura Ubushakashatsi

• , Ibiranga Ibyatanzwe. A Umwaka Bya in na Inyuma, Na:, ya: Imiterere.
• Byashyizweho kWh Bya na kW Bya, Kuva:
• Amahindukiza Himura Umuriro Ibisohoka Bya A - Gitoya.
• Imiterere y’ ibikoresho:,, na Nyuma Bya.
• Better heat-to-power: thermophotovoltaic cells, supercritical CO2 turbines and Brayton-cycle “Carnot batteries” that could lift the electricity round trip.
• Na: A Gushyingura kugirango, na na Urusobetudirishya ya:.

A

Kuri Igerageza A Gishya & Ubwoko Tangira & vendorShortName; Gitoya na Gupima. A Itangira Urugero:, OYA A.

Icyiciro	Akazi	Bikora	Igiciro	Igihe
1. Bench test	50 to 200 kg of the storage material in an insulated steel drum, a 2 to 5 kW heater, thermocouples at several depths, an air or water heat exchanger, an electricity meter and a heat meter	kg, na, Umunsi, Inyuma in	$5k to $20k	2. Kuri 4.
2.	100 or more charge and discharge cycles, materials inspected before and after	Na	$10k to $30k	6 Amasaha
3. Pilot	0.5 to 2 MWh unit on a real heat user (a greenhouse, a school, a small network), with a year of data	Bya in Igikorwa	$150k to $500k	12 to 18 months

Dukeneye

• Muhanga in Umuriro, na Umuriro Imiterere.
• Abahanga ya:,, na Ku hejuru Umwanya Birenzeho Bya.
• Abakoresha Kuri Gusangiza Ibirimo Ibyatanzwe Cyangwa Ubuturo A.
• - Kuri Udushushondanga na.
• Muyobozi ni Byakoreshejwe na.
• Na Impamyabushobozi ya: Gushyiraho, Fire na hejuru - Umwanya.

A?

Bya i Gicurasi Umuntu A ya: A. , A , - Urugero:; ya: A Nka iyi Rimwe, A Urugero: Inyuma, Na: Cyangwa ku, OYA. < X- Ngenderwaho = “Inyandiko - Imiterere” / >: NIBA i na i Imibare, Twebwe Gutangaza:% S ku i. A Urugero ni, na ni A Bya, Cyangwa.

A, Kohereza Gihinguranya i Ifishi Na: i, i Kugenzura, A Igihe, na i Igerageza. A Urugero:, Gushyiramo Ibisohoka na. i Inkomoko Ipaji iyi na i Ikindi ku i.

Inkomoko

1. 2019. Renewables 2019: heat is about half of final energy consumption.
2. Polar Night Energy (2025). Indango na Indango.
3. Solarthermalworld (2024). Kuri in.
4. M (2025). 100 ni. Amakuru
5. 2019. na Mugisha Samuel (w. Itangira: Bya (Ikigega).
6. Wikipedia Ububiko bw’umuriro, i Imisusire Imibare.
7. Ikoranabuhanga Batiri (Ikigo).
8. Akayunguruzo k’amashanyarazi Amashanyarazi (Ibisobanuro:).
9. na (2022). Bya 40%. Nature 604, 287-291.
10. ,., P. na, (2020). Bya A - Sisitemu ya: Cyangwa Urusobetudirishya. Journal of Energy Storage 29, 101382.
11. BloombergNEF (2024). - Akayunguruzo: Batiri Amafaranga Gikomeye Gukuraho Kuva 2017, Kuri $ 115 Kilowati- Isaha.
12. Lazard (June 2026). Bya Verisiyo 19.
13. Ofgem (2026). 1. Ukwezi kwa karindwi kugeza ku wa 31 Mutarama 2026.
14. Local Solar System The Fan Wall open model: the rooftop solar benchmark of $0.19 per kWh.
15. Wikipedia Andasol Solar Power Station: molten salt storage of about 7.5 hours at full load per unit.
16. Wikipedia Ububiko: i Kubika ku.
17. Urwego rw’igihugu rushinzwe ingufu (1978). Umushinga: - Umuriro amazi, Kugaragaza: Amafoto,.