The timing is right for micro-cogeneration deployment in North America. If that is the case (and even if it’s within the next three to five years), the current technology that is available is what will be used in the marketplace.

They are:

  • A product life of at least ten years.
  • The maintenance interval should be - a minimum of 4,000 hours of continuous operation.
  • It must be economical to run. As one would imagine, now that there is a market for this type of power source, the last twenty years has seen a resurgence of development of new technology products to satisfy the market. Currently there are five technologies that are used as power sources for small scale cogeneration appliances.

  • Internal Combustion Engines (ICE) - This is the most popular source of power for small scale cogeneration. It would only make sense because ICE’s have been around for over 100 years and are the most common form of power driven from fossil fuels we have - because of the auto industry. Current engines used in micro-cogeneration are just smaller versions of the same engine in the automobile - known as the four stroke Otto cycle engine. Experimentation in other forms of IC engine development is ongoing, however, the Otto cycle reigns supreme for now.

General Overview of Small Scale Technologies
There are three main components in all micro-cogeneration products: a power source, a heat recovery system, and an electrical generator. The key element of the three that differentiates these products is the power source. It was mentioned in the Background/History Page about the slow development of power sources for small scale cogeneration, but what we didn’t address is what caused this slow approach. Simply put, there are three attributes to a power source that would make it suitable for cogeneration.

  • Stirling Engines - The second most popular form of power generation used for microcogen applications has also been around for a significant amount of time - since 1816 to be exact. It was invented by the Reverend Robert Stirling and it is only in the last ten years has it been looked on as a viable candidate for a power source in small scale cogen. It is unique in design because it’s an external combustion engine, which means that heat is applied externally and not in a combustion chamber as in the internal combustion engine noted above. The history of Stirling engine production has been marked by fits and starts, and no one company has captured the market. However, because of new Stirling engine designs as well as technological advances in production methods, this engine lends itself very well to small scale cogen. Two major advantages that are brought to the forefront with this engine concept are: the ability to use many different fuels because of it’s external combustion cycle, and its ability to generate a significant amount of heat compared to other designs. These two attributes take Stirling engine research to the top of the list in new products coming to the market in small scale cogen.

"When faced with steamrolling technology, you either become part of the technology or part of the road"

- Lowell Bryan

​A Consultancy to Small Scale
​Cogeneration Markets

  • Fuel Cells - Without a doubt, fuel cells will be the power source of choice in the future for most microcogen applications. The amount of money spent on research utilizing this technology assures this will be the case. In addition, benefits received from the use of fuel cells (non-polluting, high electrical efficiency and adequate heat generation) have made it the technology of choice for the future. The current downside has to do with the costs of these systems, which will be mitigated as more product is shipped and the costs related to production improve. There are currently five types of fuel cells (which are classified by the electrolyte they use) that could be used for cogen applications, however, only two are typically known for their adaptability to microcogen use:

    • Molten Carbonate (MCFC) and Phosphoric Acid (PAFC) fuel cells are typically used for large CHP applications which they are well suited for because they are designed for continuous operation and not “cycling” applications.
    • Solid Oxide Fuel Cells (SOFC) run at a very high temperature and need time for warming up before use. Therefore they are used in continuous running applications and because of the high temps, are limited in their microcogen exposure.
    • Polymer Electrolyte Membrane (PEM) fuel cells are most common for small scale applications because they are relatively low temperature and they are capable of starting quickly with fast power response.

Lesser known power sources of the future: With over thirty companies in the world working on microCHP technology, there is an excellent chance that some of these “little known” technologies will be successful as the marketplace develops and opens up to new ideas.

  • Organic Rankine Cycle - A number of companies are in the late development stages of testing an ORC product. This technology is mostly common in larger units (140kW to 2500kW) however, small residential sized appliances are on the horizon. This unit utilizes a boiler that heats an organic fluid with a low boiling point. The steam is generated from the boiler and is used to drive a turbine which is coupled to a generator. The steam is condensed and then sent back to be reheated and complete the cycle.
  • Microturbines - Microturbine development is moving forward at a rapid pace based on the fact that “base” units have already proven successful. By base units, we mean that there are successful products utilizing microturbines as the source of power, however, the smallest viable unit is a 30kW unit manufactured by Capstone, but the marketing and sales effort is very limited. (The next size available is 65kW which takes it out of the range of our technology.) A number of companies are developing microturbines with a power output of less than 10kW, but they are in the early stages of development. More than likely, this technology will be viable within the next five years.
  • Internal Combustion Engines with “exotic” power cycles - Forgive the descriptor here but there are many IC engines in garages and test labs that are under development for many applications, one of which could be small scale cogen. We are aware of a number of these, but for the most part, these are strictly prototypes and early test units and at this time warrant only a comment and no real focus or interest.