Heat Engines and Heat Pumps

New Heat Pumps developed at Sencera. No refrigerants, low maintenance, competitive cost.

There is an underreported environmental issue with air conditioners and heat pumps. All existing systems use a gas cycle that relies on special refrigerant materials that change phase cyclically between liquid and gas at desired temperature and pressure. However, these refrigerants are hazardous to health and the environment and are the subject of several multi-national agreements to regulate and eventually ban their use. Even so, just considering existing installed systems, refrigerant leaks and energy use in these devices represent “around 10% of global CO2 emissions.” (Maidment, 2017, National Institute for Public Health and the Environment in The Netherlands)

A 30 percent efficiency improvement, with a phase-out of hCFC’s and CFC’s used in these machines would eliminate the need for 1,550 peak power plants. Such a solution would have a bigger impact than several well-known renewable energy projects:

  • 8 times the effect of China’s Three Gorges dam
  • 2 times India’s entire solar initiative.

By the year 2050 for the globe as a whole, the total avoided carbon dioxide equivalent emissions would amount to some 4 billion tons annually — more than any single country other than China and the United States — with 1 billion tons of emissions avoided in India alone. (Shah, et al. 2017, Lawrence Berkeley National Laboratory)

Stirling engines have a 200 year long history. They are reversible – meaning they can used to move heat if mechanical work is available or to produce mechanical work from heat flow. The theory of these systems is well-developed. (See, for example, the thermodynamics pages of Ohio University, or Martini’s book).

Sencera has been involved with Stirling for over a decade, including past work with Sunpower (now part of Ametek) and Renovalia. Present work continues with MEC to help refine a 1 kW Stirling engine and to develop newer, more cost effective systems. The MEC engines have almost 500M accumulated run hours, the most of any design of which we are aware.

MEC 1 kW Engine

In 2016, Sencera received an innovative research award from the ARPAe GENSETS program (part of the US Department of Energy) for some if its work on Stirling engines.

Present development is focused on lowering the production cost of Stirling devices to make consumer appliance level devices feasible.