The Hippo


Jun 26, 2019








Coming to a government building near you?

Legislation approved by the New Hampshire House (pending a committee vote) would allow one of the NRG-branded generators to power and heat a to-be-determined government building as a test and public demonstration.
“We do appreciate Sen. [Jeb] Bradley’s initiative on this legislation. It’s something that we’d like to [try] here in New Hampshire and improve it here in New Hampshire,” Toohey said. “We think it’s a great initiative with zero cost to the state [to] demonstrate advanced New Hampshire technology and take us to another level of energy development.”

Gas to power your home
DEKA perfects base generator technology

By Ryan Lessard

The Stirling engine concept celebrates its bicentennial this year, just in time for people to start learning what the heck a Stirling engine is and how it could be the missing link in home electricity generation. New Hampshire inventor Dean Kamen and his R&D firm, DEKA, have been tinkering with the engine for decades and say it’s finally coming of age now that engineers have overcome longstanding efficiency problems.
Invented in 1816 by its Scottish namesake, Reverend Robert Stirling, the Stirling engine was developed as an external combustion engine to rival steam engines. 
The way it works is actually very simple. One end of the engine is cold while the other is hot, and the air (or another gas) in between moves pistons from the expansion and contraction of the air caused by the interplay of hot and cold. The process is considered “external combustion,” as it’s the heat, not the pressure from the small explosions harnessed by internal combustion engines, that powers it. Jim Scott, DEKA’s head of business development, says that’s what makes it a cleaner source of energy.
“The beauty of a Stirling engine is its external combustion,” Scott said. “This is more like a gas burner on your stove.”
One of the things that makes Stirling engines unique is that the excess heat produced by the engines can be recaptured, stored and reused for energy — a process called regeneration.
Over the generations that followed, small improvements were made, like using different gasses. But it was not efficient enough to compete with new internal combustion and electric engines.
That’s where DEKA comes in. 
“I can tell you the Stirling cycle has always been a passion for … Dean Kamen,” said DEKA Executive Vice President Brian Toohey.
He said Kamen has long been enchanted by the technology’s potential for environmental friendliness, longevity and applicability in vehicles and homes.
Scott estimates there have been about 20 generations of Stirling engine prototypes going back about two decades. 
In 2008,  Kamen unveiled a Stirling engine-powered hybrid car, but the focus now is on creating base generators for homes, apartment complexes and small businesses. 
Through a partnership with NRG Energy, DEKA designed and assembled about 20 prototypes of the current iteration of generators, which Scott says have an overall efficiency greater than 85 percent when used for both power and heat. In other words, it can cut down overall fuel use and greenhouse gas emissions by about 20 percent.
It uses helium gas as the “working fluid” and the burner is fueled by natural gas, though Toohey says it’s designed to work with propane and home heating oil as well.
Toohey said the advances DEKA made to the Stirling engine that fixed inefficiencies did not come from one major invention.
“It has to do with the use of certain materials. It has to do with the types of gasses involved and the whole range of the types of fuels that are used — a whole range of items,” Toohey said. 
DEKA folks think the NRG generator, which produces up to 10 kW, is going to be just the right size and capacity for the market they’re aiming for: distributed energy production.
People interested in weaning their home or business from its dependency on the grid have turned to solar panels and, in some cases, windmills. But those both suffer from being intermittent sources of power that dry up when there’s no wind or sunlight.
Toohey says a Stirling engine could fill that gap.
“Ideally, ours could be a solution to enable distributed energy in a way where you don’t have the intermittency problem,” Toohey said. “Our system, we believe ultimately, could be the glue that sort of brings those things together, because when those aren’t available, you can use propane or natural gas or any sort of fuel to create electricity.”
While no one can say what the price for such a generator will be just yet, Toohey says it will be competitive once it’s mass-produced, which is something he hopes will happen soon. 

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