A Zondits Interview: Ilios Dynamics Brings Efficient Water Heating to the Market

Ilios Dynamics
Jesse Remillard, ERS, for Zondits. April 13, 2016. Image credit: Ilios Dynamics

Zondits recently had the opportunity to speak with Stephen Lafaille, the product manager for Ilios Dynamics. The company manufactures a line of natural gas engine-driven heat pump water heaters and is a subsidiary of Tecogen Inc., a leader in the CHP market for over 30 years.

Natural gas-engine driven heat pump water heater is a mouthful. Can you describe what the Ilios products are and how they work?

Indeed it is.

Tecogen created its subsidiary Ilios Dynamics to bring to market a much more efficient solution for water heating. While Tecogen’s traditional cogeneration products are indeed efficient, they do not have an operating cost advantage in all parts of the country. There are many areas where electricity is very cheap, and competing with the grid can prove difficult.

For this reason, Tecogen sought to create a product using the principles of combined heat and power (CHP) technology. But instead of cogenerating electricity and hot water with a prime mover such as a natural gas reciprocating engine, the Ilios product line uses the prime mover to drive a vapor-compression cycle, and the resultant waste heat is recovered and added to the heat created from the refrigeration cycle, e.g., condenser heat. So you are leveraging what is called work-assisted heating to heat a fluid, rather than the simple burner-in-a-box methodology that traditional boilers and water heaters utilize.

In Tecogen’s opinion, if you are going to produce an engine-driven heat pump product and ensure that it reduces not only operating costs but also energy use and therefore greenhouse gas emissions, then the engine waste heat must always be fully utilized. In our minds, there is only one type of heat pump that can always make use of the engine waste heat, (which happens to be easily recovered in the form of hot water) and that is a heat pump water heater. It is a natural fit.

Ilios DynamicsWhat are some of the differences between engine-driven heat pumps and standard electric heat pump water heaters?

A lower operating cost and increased efficiency are the two main advantages. The idea of using an electric heat pump to heat water is great. It is one of the most efficient ways we can heat water, but one of the drawbacks can be that although it is very efficient, it isn’t necessarily cheaper to operate. Electricity is generally about two to four times more expensive on a per-energy-unit basis than natural gas. So, in most areas it is unfortunately cheaper to use more energy and heat water with an 80%-efficient natural gas boiler than it is to heat water with an electric heat pump.

The natural gas engine-driven heat pump combines the best of both worlds. We can make use of the inherently efficient heat pump cycle, but drive that process with low-cost natural gas. This reduces energy use and can also make a big impact on operating costs compared to a traditional boiler or electric heat pump water heater. Also, because we are recovering the waste heat from the prime mover, we are taking the power generation process, which is around 30% efficient, and bringing it up to the low-80% range. This is where the carbon savings advantage comes in compared to an electric powered heat pump.

Are the maintenance requirements different for engine-driven heat pump water heaters compared to standard heat pump water heaters?

Yes, but only due to the requirements of the engine. The refrigeration cycle is almost identical; we just use a different type of compressor, one without an integral electric motor. However, engines these days are very advanced and reliable and have very little preventative maintenance requirements. We service our engines annually, and we are connected remotely to all of our products either through the Internet or via cellular connection. It’s similar to how your car can be checked at the inspection station via its on-board diagnostics port. We are doing the same thing to our equipment, but it is all done remotely, and the data is stored in the cloud and we can access it from anywhere. Our service techs can check out how a machine or engine is operating right from their smartphone.

What types of natural gas engine-driven heat pump water heater products does Tecogen offer?

Tecogen offers both an air-source and water-source version of its Ilios natural gas engine-driven heat pump water heater. The air-source product is pretty neat because it moves heat from the air into the water and adds heat from the engine block, exhaust, and oil, which improves efficiencies up to twice those of a traditional water heater. It also has its own integral generator that cogenerates all of its parasitic loads for fans and pumps, which is not only the most efficient way to drive those motors, but also the most cost-effective.

The water-source product is equally interesting because there are so many different ways it can be applied. For example, it can be applied to simultaneously heat and cool, or it can recover energy from a condenser water loop and then heat the DHW in that same building. It can also recover energy from a low-grade waste heat source being rejected in a manufacturing facility and use that waste heat to heat process water, or it can be applied in a geothermal or “ground-source” system.

Ilios DynamicsCan you tell us a little about what kind of applications and scenarios engine-driven heat pump water heaters excel in? Are there any case studies you can talk about? What kind of simple paybacks or returns can your customers expect to see?

We find that sites that have a large consistent need for hot water are the best fits because the more hours the unit can operate each year, the more energy it can save, which leads to a better ROI for the customer . Some of these candidate buildings include large multifamily residential with centralized hot water, plus dormitories, hotels, hospitals, nursing homes, health clubs, etc. Also, many of these buildings are simultaneously heating some water – i.e., for domestic hot water, pools, reheating for humidity control – and they are simultaneously cooling the building. That means there’s a great opportunity to leverage our water-source natural gas engine-driven heat pump to simultaneously heat and cool.

We have a lot of great applications. For one, we are heating and cooling the Forest E. Mars Jr. Athletic Center at the Hotchkiss School in Connecticut. We have seven of our units at the world renowned Scripps Research Institute that are simultaneously heating and cooling. We also have several units in Ireland heating schools and hospitals with our air-source heat pumps.

Whatare some of your favorite things about engine-driven heat pumps?

I am a fan of heat pump water heatingin general. It is pretty clear that boilers are an age-old technology, and there are much more efficient ways to go about heating water. A heat pump is one of them, but there are inherent disadvantages with the costs of electricity, and the compression required to create useful hot water.

The natural gas engine-driven water heater uses cheap natural gas, and because of the high-grade engine waste heat, the outlet water temperature can be boosted to fairly high temperatures without relying on the heat pump compression alone.  Additionally, from a primary energy use standpoint, the natural gas heat pump has a greater reduction in carbon footprint.


Where do you see the future of engine-driven heat pumps going?

I think you will start to see more and more of them, but only engine-driven heat pump water heaters, as they have both an operating cost and energy efficiency advantage. Any other type of engine-driven heat pump, such as one that does space heating or cooling, may not always be able to utilize the engine waste heat. When the engine waste heat  is not being used, there is still an advantage in the difference in cost between electricity and natural gas, but no overall energy efficiency improvement. In order for this technology to be widely accepted we need to make sure it has an energy efficiency benefit to go along with the operating cost benefit. That is the biggest thing people often forget.