© Photo | James Andrews/ebm-papst

Not just heat

The new boiler from the British company Flow­group is not just any old boiler. It doesn’t just produce heat, but elec­tricity too, and pays for itself in the process. The story of an extra­or­di­nary project.

Geoff Barker turns the tap and smiles. Not just because there is warm water coming from the tap. You’d expect that from any new boiler. He’s smiling because he knows he’s saving money. From the outside, the compact device hanging on Barker’s wall does not look any different to a normal gas boiler. It saves space and gener­ates heat for water and central heating. But it also gener­ates elec­tricity. This kind of simple micro combined heat and power unit (short:micro-CHP unit) is the first of its kind.


All lined up: The micro-CHP units have to pass numerous tests in the lab.

The little magic box, from the Flow­group in Chester in north-west England, has been avail­able since the start of the year on the British market under the name Flow, intended for larger house­holds. If Barker were a normal customer, he wouldn’t even have to pay for the unit. The deal works as follows: anyone wishing to purchase the Flow only has to pay the instal­la­tion costs. They also take out finance for the cost of the Flow and signup to Flow­group for their elec­tricity and gas. After this, the customer receives a rebate through their energy bill to cover the cost of the finance, all made possible by the local low cost elec­tricity gener­a­tion. After five years, the Flow has paid for itself and the elec­tricity produced results in energy savings for the owner.

From start-up to success

Barker isn’t a normal customer, however, the device on his wall is only for test purposes. He is Busi­ness Devel­op­ment Director at Flow­group and was involved in the devel­op­ment of the Flow from the begin­ning. Getting the product ready for full produc­tion was a long journey. The busi­ness began in 1998 with the busi­ness model of devel­oping new energy tech­nolo­gies and then selling them to other compa­nies.

The Flow’s story begins in 2006. “Orig­i­nally, we just wanted to develop new, cost-effec­tive tech­nology for a micro-CHP unit, which we then wanted to sell to heating appli­ance manu­fac­turers. But during the devel­op­ment process, we decided to take full control of the produc­tion and marketing”, explains Barker. This was no small venture for a company that had never built a boiler itself before. Even the tech­nology it was based on had never been used in this form.


The boiler takes up little space in the home.

The inverted refrig­er­ator

The tech­nology is similar to a cooling cycle in a refrig­er­ator, which obvi­ously has little to do with a gas boiler. One aims to remove heat while the other has to generate as much of it as possible. The designers turned the cycle prin­ciple on its head and the Flow boiler now works in precisely the reverse manner with the so-called Organic Rankine cycle. This process has previ­ously been used in geot­hermal or solar power facil­i­ties. Other manu­fac­turers use expen­sive solu­tions in these devices like Stir­ling engines or fuel cells.

“During devel­op­ment, we decided to take produc­tion and marketing into our own hands.”

Geoff Barker, Busi­ness Devel­op­ment Director at Flow­group

By contrast, the Flow essen­tially func­tions like a normal gas condensing boiler, except that instead of water, the combus­tion heat evap­o­rates a special fluid with a low boiling point. This fluid is similar to the cooling fluid in a refrig­er­ator. The vapor that this creates drives a scroll, which acts like a mini gener­ator and produces elec­tricity. Once the vapor has fulfilled this task, it enters a heat exchanger where it heats the water. The vapor condenses back to a liquid and the cycle can begin again. A pump keeps it moving through the system.

That’s the theory. In prac­tical terms, this meant a lot of devel­op­ment work. “Most of the work went into devel­oping the pump, which is the key compo­nent for the cycle”, explains Barker. This is because the pres­sure and the speed at which the pump drives the fluid are deci­sive for the Flow’s perfor­mance. The motor for the pump must be able to cope with high and low pres­sures, without heating up too much. As the boiling point of the fluid is very low, the motor cannot heat it up too strongly, as the vapor bubbles created would damage the pump.

Exper­tise from the conti­nent

At around the same time, the engi­neers at ebm-papst in Land­shut were working on a new motor for fans. When Paul Prescod, Commer­cial Director at ebm-papst Auto­mo­tive & Drives UK, found out about this project at a presen­ta­tion, he imme­di­ately thought of the drive for the pump which the engi­neers at Flow­group had asked him about. “The motor from Land­shut may not have been devel­oped for this kind of appli­ca­tion, but its char­ac­ter­is­tics were a pretty good fit to the require­ments”, remem­bers Prescod.


Working closely: Geoff Barker (middle) discussing motors and fans with Paul Prescod (right) and Steve Durant from ebm-papst UK.

His colleagues in Land­shut were quickly convinced and produced a proto­type of the motor, which would later be launched on the market as the BG43. The EC motor was an instant hit. “It was exactly what we were looking for: a highly effi­cient and compact motor”, says Barker. It was the begin­ning of an inten­sive coop­er­a­tion. “We devel­oped many different proto­types of the Flow and ebm-papst supported us in every new devel­op­ment step with their exper­tise”, explains Barker. In the end, an Italian company was chosen to produce the pump. “As we are also active in Italy, we were able to go along with this step with no prob­lems and support the work there, too”, empha­sises Chris­tian Diegritz, Head of Sales Depart­ment at the Land­shut plant.

The plant gave the devel­op­ment of the project signif­i­cant support. But this support was not just limited to the motor. Flow­group also chose to use the NRG 118 blower from ebm-papst. That was music to the ears of Steve Durant, Senior Consul­tant at ebm-papst UK, who was respon­sible for this compo­nent. “We were now able to offer the motor and blower in a single package, which further reduced the costs for the Flow.” No small matter when you remember that the Flow aims to be an afford­able solu­tion.

A clever busi­ness idea

After count­less tests and certi­fi­ca­tions, the micro-CHP unit kept making progress. In 2013, the ques­tion for Flow­group was how to best get the mini power station into house­holds. The slightly unusual answer was to use their own energy company. “We founded a subsidiary which provides customers with gas and elec­tricity. This gave us a customer base to act as poten­tial buyers of the Flow”, says Barker of his some­what different busi­ness idea. Customers will be able to profit from this from early 2015 in a range of ways.

The device is compact and easy to install. “We designed the Flow so that it could be installed on the wall by heating special­ists with minimal training”, explains Barker. Here, it produces around 2,000 kilo­watt hours of elec­tricity in addi­tion to heat. This corre­sponds to half the consump­tion of an average British house­hold. Once the Flow has paid for itself after five years, the consumer there­fore saves around 50 percent of their elec­tricity bill. The Flow is currently only avail­able in Great Britain. “We are already in talks with energy compa­nies in other coun­tries to intro­duce the micro-CHP unit there”, says Barker.

Smart elec­tricity

smart_electricityThe gas-fired combus­tion chamber heats a special liquid compa­rable with the refrig­erant in a refrig­er­ator.

The resulting steam drives a gener­ator that produces elec­tricity. Then the hot steam heats water in a heat exchanger and condenses.

The liquid is pumped back to the combus­tion chamber and the cycle resumes.


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