STOCKHOLM --- It’s Christmas in July, as far as your hot water heater is concerned.Seec
, a five-year-old company in Stockholm, combines solar thermal technology with geothermal to effectively allow commercial buildings to bank summer heat until winter. It can also be employed to exploit the chill of winter to run air conditioners in summer.
The system -- technically called borehole thermal energy storage -- can cut heating and hot water bills by 70 percent to 90 percent, says CEDO Andreas Andersson, and will pay for itself in 3.5 to 5 years. The company has installed a few systems in municipal buildings here and has licensed it to a Norwegian company for use at an industrial site.
“In the last four to five years, it has really taken off,” he said.
Other companies have erected similar systems at three Ikea stores here. A local hospital gets all of its heat and hot water from a borehole system.
Borehole technology has been around for decades, but conventional systems lose about 30 percent of their energy in storage. Seec’s secret sauce is found in software and sensors that help reduce losses to almost zero. The company analyzes the geology of a site, projects the local heat retention capabilities and then orchestrates when and how to capture and deploy the heat during the year.
In a sense, Seec is a storage-as-software play. While the company sells hardware, it also can provide it as a service.
Here’s how it works. Solar thermal collectors trap heat from the sun in hot months. The heat is injected into a water/alcohol or water/glycol mixture and then is stored in an array of boreholes ranging from 150 meters to 300 meters deep. (After 500 meters, the drilling expenses get too high. The temperatures and well depths are also far less extreme than those used in geothermal systems that produce electricity instead of heat.) The boreholes, essentially wells, are spaced four to five meters apart in concentric circles.
Unlike conventional geothermal systems, the water/glycol mixture does not absorb energy from the earth. Because of the close proximity of the wells, taking heat from the earth would just freeze the ground.
“The earth is just containing it,” Andersson explained.
The fluid is stored at a temperature between 7 and 12 degrees Celsius. When it’s needed in the summer, the fluid gets brought to the surface and run through a ground source heat pump, which amplifies the heat so that the customer ultimately gets water in the 65 degrees Celsius range.
The fluid, now stripped of its heat, gets re-injected back into the earth. In summer, the reverse process occurs: somewhat cool fluid is passed through the heat pump to run the air conditioner.
The technology works best in areas with extreme swings in temperature between summer and winter.
“It does not work at the equator,” Andersson noted. “The bigger the temperature difference, the better.”
Sweden, naturally, is a pretty good test market. The country consumes 40 terawatt-hours of energy per year for heating and hot water, a bill that comes to around 40 billion kroner, or $6.5 billion in U.S. terms. (I’m here this week at a conference on technology in the region.)
Will this technology ever come to the States? It would work well in the Midwest and Northeast. Nordic countries -- Sweden, Denmark, Estonia, Finland and Norway -- are all gearing up to sell their know-how in efficiency and energy production accumulated over the last few decades worldwide. Innovation Center Denmark and others will host a smart grid symposium next week in Palo Alto. But economic feasibility might depend on the various local incentives for renewable power and storage.
Still, the economics so far look promising. Power and heat are fairly cheap in Sweden. The country gets most of its power from hydroelectric dams or nuclear plants. Power costs about 1 kroner, or 15 cents, per kilowatt-hour.