Graph of the pit thermal energy storage site in Hyvinkää, Finland, showing cross section of the pit, civil construction with lining, water piping with entry diffusors and insulating top layer cover.

There's another #SeasonalStorage project in Finland breaking records, the Hyvinkää #PitThermalEnergyStorage:

Pit Volume 380.000 m3
Area 225 x 165 m
Depth 20 m
Water temperature 40 - 90 °C
Capacity 18.000 MWh
Discharge max 60 MW
Cost 33 mil. €
In operation: Fall 2027
hlv.fi/lampovarasto...

Varanto - The Cavern Thermal Energy Storage - Vantaan Energia The World's Largest Cavern Thermal Energy Storage

The technology of #Varanto, the 90 GWh #CavernThermalEnergyStorage project in Vantaa, Finland, was't investigated, obviously due to different geology in Nuremberg.
The #PitThermalEnergyStorage option could store 160 GWh but require twice the volume, 2 million m3
www.vantaanenergia.fi/en/about-us/...

Table of heat storage technologies, with typical technical and economical parameters

The study covers several #ThermalEnergyStorage technologies:
#PitThermalEnergyStorage
#BoreholeThermalEnergyStorage
#AquifierThermalEnergyStorage
#PackedBedThermalEnergyStorage
(= #SandBattery)
and others like latent, multilayer, sorption, Ruths and methanisation

www.evt.tf.fau.de/files/2025/0...

Aerial photo of the excavation of the 20.000 cubic meter thermal energy storage pit.

Picture of solar thermal collectors, total surface 12900 m2

Diagram of the system showing collectors, heat storage, buffer storage, Wood chip boiler and heat pump

Example of solar #DistrictHeating cooperative in Germany
#SolarwärmeBracht.
12.000 m² #solarThermal collectors
20.000 m³ #pitThermalEnergyStorage 🇩🇰 style
Solar fraction 70%
#heatPump +Biomass boiler
130 households, total 2.7 GWh/a
Price 60€/month + 16 ct/kWh
www.solarwaerme-bracht.de/faq/