Fifty homes in the Netherlands are now able to generate electricity as well as heat their homes via their boilers. Energy producer Eneco has installed 50 HRe boilers - ordinary heating boilers with a built-in generator - as part of a field test to determine if decentralised energy production works in practice. Of course, the company also wants to see if it's profitable.

Eneco spokesperson Saskia Streekstra explains how it works:

"The HRe boiler functions like a normal high-efficiency boiler, producing warmth and hot water, but it is unique in that it also produces electricity. Everything that occurs within the home that has to do with using hot water or heat sends a signal to the gas motor in the boiler to start producing electricity".
 

The generator is a Stirling engine; electricity is produced through heating and cooling gas within the closed-circuit chambers in the engine. The process is known as the Stirling cycle. As boilers produce warmth in abundance, it costs just seven percent more gas to produce electricity.

Huge savings
The savings are enormous: experts estimate that it could deliver savings of up to 400 euros per year per household. It also reduces carbon dioxide emissions by more than 1200 kilogrammes per year.

Frank van den Brink and Vera van Dam from Utrecht were the first people in the Netherlands to get an HRe boiler. It has been working for a month and Frank is fascinated by the meters:
 

"I've produced 17 kilowatts of energy this month, but it is summer so the boiler has only been producing warm water for the shower. I'm really curious to see what will happen this coming winter when the heating is on all the time. It'll start generating electricity like a mad thing."

Highly efficient
The HRe boilers are extremely efficient when compared to large power plants. Just 50 percent of the energy that enters an electricity power plant in the form of natural gas or coal leaves the power plant in the form of electricity. The other 50 percent is lost in heat from the chimneys, by friction in the generators or is lost as resistance heat. Compare this to the 98 percent efficiency rating of the HRe boilers and the picture becomes clearer.
 

Eneco is not a charity, and neither are the numerous energy producers across the world who are investigating decentralised electricity production. They all want to continue to earn money in the future, however, if HRe boilers become commonplace, then customers will only pay for the initial purchase and maintenance. A monthly bill will still be sent out but hopefully, it will be considerably lower.

How the Sterling engine generator works: