1428-1870: Very High Efficiency Natural Gas Heating, Home Backup Generator, Distributed Power Grid Generation and Local Grid Stabilizer


ARPA-E Contact: None.
Technical Subcategory: 2.2 Thermal-Thermal
Funding Request: $500,000 Funding Request.
Project Duration: 12 Month Project Duration.
Project Abstract: Home heating using Natural Gas is common, however direct heating is not the most efficient heating method since at lower temperature differences, heat pumps are more efficient. Natural Gas is often used for Central Power Generation, however the waste heat cannot usually be used effectively. This project creates a very high efficiency home heat management system that uses natural gas to run an electric generator, that can run a heat pump, captures most heat that is generally lost, can produce flexible distributed grid power that can be more reliable then central power, reduce the power distribution loses, and eliminate the lost heat of Central Power Generation. Even though combine cycle generators can achieve up to 50% to 60% efficiencies, the huge savings per home can greatly reduce consumption for the same home heating result.


The huge US energy usage will be reduced by retrofitting a very common, home high energy usage system, which will greatly improve energy usage efficiency while providing the future ability to stabilize local power grids from the destabilizing solar and wind power energy.

This will enhance the economic and energy security of US by (i) reducing import of foreign energy by making usage of natural gas more efficient, allowing saved natural gas to be used for other needs. (ii) Reductions of emissions including greenhouse gases, are from using natural gas more efficiently for the net end work and allowing the saved natural gas to be used to displace more polluting fuels. (iii) Improves energy use efficiency in the home energy sector. Development and deployment of this very high efficient technology helps ensure that US maintains a technological lead in developing and deploying advanced energy technologies.


Where natural gas is available, natural gas is generally used for home water heating and home central heating. Sometimes the home heating system also includes a heat pump.

The current practices is undesirable since 1): For lower heat differences heat pumps are more efficient then direct heat. 2): Natural gas cannot directly be used to produce electric power to run a heat pump without a generator. 3): Current home systems do not have computers to optimize heating operation. 4): Current home natural gas electric generators are light weight, noisy, and do not collect and conserve heat, do not have grid matching inverters, and do not have computer control to allow integrated home and smart grid coordination.


The new idea is a new home heating and power generation system that more effectively uses the energy of natural gas, reduces the amount of power needed to heat the house and water, provides electric power generation for both the home and also for potential power grid load balancing and distributed power generation, and puts the home on the smart grid path.

Shown in Figure 1: Very High Efficiency Natural Gas Home Heating System, is a block diagram of the components. Most of the components have insulated operation areas to minimize heat loss.

Natural Gas Home Heating System

Figure 1: Very High Efficiency Natural Gas Home Heating System

The natural gas powered engine is designed for optimal operation in this environment, which the computer can control power output from low to maximum power. It is a high reliability design that is very quiet with the exhaust flowing through the high temperature storage and then through the primary hot water heater to quiet and absorb maximum amount of exhaust heat. It has a cylinder and heads that can operate up to >150C instead of traditional 90C to support absorption refrigeration home cooling and additional heat saving capacity when running the generator has advantages, as in the case that selling excess output power on the grid is an advantage. The high heat storage absorbs the heat from the top of the engine and uses a non toxic substance like cooking oil to operate at the higher temperature. A computer controlled thermostat is used to control the flow and heat transfer from engine. The top of the engine is in the same thermal insulation area as the high temperature tank. Heat is transferred to the primary tank as needed.

The bottom of the engine is thermally separated from the top of the engine, including a thick insulating gasket between block and cylinders, which bottom heat goes directly to the primary water heater, on engine shutdown heat is transferred to equipment staging tank.

Water enters the system through the Environment Staging Water Heater. When the water temperature is below the external home temperature, hot days have larger differences, heat is brought in through an outside heat exchanger (pump not shown), at low energy costs.

Water from the Environment Staging Water Heater is fed to the Equipment Staging Water Heater where waste heat is collected from the generator, inverter, and from post shut down of motor. When conditions are right, a heat pump can be used to favorably increase temperature before being fed into the primary water heater.

The high quality generator provides multiphase ~280V electric power to the inverter. At 95% efficiency at 10KW, the generator generates 500 W heat loss rate which is saved in Equipment Staging Water Heater for near 100% energy usage (excluding small insulation heat losses).

The central heating includes heat pump, gas heat for backup and very cold days, water heat and high heat exchangers for when tanks have reached heat capacity and house heat is still needed.

Current concepts include smart grids, home power generation, power management with some general management and small solution cases, but they do not provide overall integration, falling far from being ready for a full local smart grid. This develops the full heating and power solution for optimal energy efficiency for the natural gas solution that can replace current equipment with future integration into a smart grid, making the home system ready for smart grid operation.

If successful, state of the art of update and deployment of primary home energy usage equipment will help US maintain a technological lead in developing and deploying advanced energy technologies since a new home energy management technology will greatly improve overall energy efficiency, lower energy usage, and cut greenhouse gas output across the system.

  Efficiency Heat Net Saved Loss Notes
Central Generator 50%-60% (Combined-Cycle)       40%-50% Not Including Grid Transfer Losses
Gas Water Heaters 70% - 85%         Water Heater Efficiency (Includes time lost energy)
Gas Furnace 80% - 95%         General Furnace Efficiency
Generate Electricity 30% 60% 90% 60% 10% After generation heat is stored in hot water tank.
Heat Pump 200%-300%         Efficiency is related to temperature differences
Gas Gen to Heat Pump 30%*200%=60%, 30%*300%=90% 60% 120%-150% 20%-50% 10% Just heating portion.

The best central natural gas generators loose 40% to 50% of the energy to waste heat, with additional loss in the electric grid during distribution where 6% to 8% loss is considered normal. The water heater efficiency includes output of water and heat loss over a 24 hour period, so is a different definition than general heat loss and efficiency. All other efficiencies in the table is the instantaneous process definition. The local generation of electricity allows the waste heat to be stored in the hot water heater and gives an advantage over lost heat at a central power plant. When the electricity is being generated, it can be used to run a heat pump and gain the thermal advantage of more home heating with less energy, smaller temperatures difference gives better efficiency, and efficiency goes down for temperature increases. Using the Natural Gas to create electricity to run the heat pump furnace gives net 20% to 50% improved energy utilization. Heat pumps do not work well for high temperature differences, which is why direct heating is almost always used in the primary water heater . The generator output heat can be used to heat the water and when the full heat capacity of the water heating system has been reached, the extra heat can be used for home heating. A water tank heat pump works best on an intermediate temperature water tank and when external warm temperatures are high.


There are very few technical risks. All work can be done with current technology. Smart grid technology is a moving target. The control system and power inverter may not meet all needs of future unimplemented and unknown needs, but this system greatly moves towards a smart grid.

There are no high risk innovations, fabrication, and subcomponent performance. The primary innovation is electric generation, heat management, staged heat storage, and inverter.

Natural gas is delivered by Therm, which has 105.5 MJ and is equivalent to 29.3 KWh of power. My recent Natural Gas bill cost is $0.84733 per Therm, which is $0.02892 per KWh of equivalent resistive electric heat. This system costs more than the standard system. When the cost and energy savings are significant enough to justify the additional cost, then the economic advantage justifies change over. Indirect advantages include multiple electricity and heating sources, allowing heat source selection for best economics, and home operation during either utility outage, energy cost advantages for grid stabilizing during times of low or quickly changing solar and wind energy input, and insurance of lower energy costs if a big shortage greatly increases gas and/or electricity costs.


The goal is a full prototype with 10 KW generator with better than 90% heat capture and a document of tradeoffs, system component economics, and performance test results.

The work will include the system design with available component tradeoffs. Will try to find suitable generator, but design and build if necessary. Find a suitable production motor to modify to move towards target operation (150C) operation with split top and bottom temperature operating range. Design and create dynamic loadable, with phase resynchronization, grid capable inverter. Use general purpose PC computer to write the control and monitor programs and run experiments. Run detailed experiments determine the performance and effectiveness of each of the components. Do analysis and a detailed study to determine performance improvements compared with typical installations. Consider usage in several environment where Natural Gas is commonly used. Do component cost and trade off studies to determine rules for economic and energy performance tradeoffs. For example, absorbent cooling system might not have good value in Vancouver WA, but may be very desirable in Phoenix AZ. Different areas and needs may have different optimal tank sizes.


The project will be managed and developed by Mike Polehn, 30 years engineering experience, BS of Computer and Electrical Engineering, OSU (Oregon). Education included mechanical engineering statics, dynamics, strengths, thermal dynamics , etc. We will hire ME collage students locally from WSU (Vancouver) part time and/or paid interns to enhance their education experience.