District energy
Aalborg’s thermal storage offers lessons for Nova Scotia
Seawater heat pumps and large hot-water tanks show how district heating can store renewable energy for later use.
Originally published on LinkedIn, sharing commentary on Jan Rosenow’s report from Aalborg. Costs and storage capacity below are approximate estimates from the original post.
An interesting district heating project in Denmark: Aalborg's district energy system, which serves about 120,000 households, will draw heat from the sea using four 44 MW industrial seawater heat pumps from MAN Energy Solutions, 176 MW in total. The heat pumps and electric boilers will take advantage of low electricity prices, including periods of abundant wind and solar generation, to produce heat that can be supplied directly to the district heating network or stored in four large hot-water tanks for later use.
The price tag: • Total program: about CAD $560 million, covering the heat pumps, a 150 MW electric boiler plant, heat storage and site infrastructure • Seawater heat pump plant (177 MW): ~CAD $360 million, or about CAD $2 million per MW of heat • Four hot water storage tanks (200,000 m³): ~CAD $86 million
By my rough estimate, those tanks store around 10 million kWh of heat. That works out to about CAD $8 per kWh of storage capacity, a fraction of what battery storage costs per kWh. It's not an apples-to-apples comparison, since the tanks store heat rather than electricity, but it shows why storing energy as heat is such a cost-effective way to soak up cheap wind power.
We should be considering large-scale thermal storage in Nova Scotia as it pairs nicely with our cheap wind energy and heating-dominated climate.
