Egenolf Micro Combined Heat & Power (mCHP) for Off-Grid power systems :
The following might be of interest for your stand alone off-grid power operation.
A typical off-grid power system contains a battery bank, a battery based inverter, Photovoltaik and a back-up generator. During the fall and winter month with short days the generator is supplementing the system with electricity needed to charge up the batteries.
The weak point in such a hybrid system is the inefficiency of the power generator. Electricity produced by a conventional (diesel, gas or propane) generator is only utilizing 30-40% of the input fuels energy content. The balance 60-70% of the energy content is ending up as unused waste heat. During the times of the year, when you have to run the generator, its usually heating season as well. So why not utilizing the waste heat, store it and heat your house, shop or camp and saving on your heating fuel (wood, oil, propane)
During and in addition to my work for the NRC's IRAP in the last two years, I have developed a stand alone Micro Combined Heat & Power system, which is controlled by either the demand for power or for heat, whichever comes first.
By doing so, the total efficiency increases to between 85% to 90% depending on fuel type and generator used compared to 30% to 40% for conventional generators.
How it works :
The thermal energy of the coolant from the liquid cooled generator engine as well as of the exhaust gas are captured with special designed hydronic heat exchangers and stored into a large buffer tank.
Thermostatically controlled heat loads withdraw the stored heat from the buffer tank on demand. If the stored heat in the buffer tank reaches its lower threshold the generator automatically starts up (Heat Mode), charging up the buffer tank with heat.
At the same time while the generator is running the battery bank gets charged up and an automatic transfer switch supplies power to the connected electrical loads.
In case the the demand for charging up the batteries comes first (Power Mode) all the waste heat from running the generator is stored in the buffer tank for future heat demand. The buffer tank is designed to store enough heat for a typical generator running cycle, without having to direct additional heat into a dump load in order to avoid overheating of the system. Extremely efficient insulation keeps the heat loss in the buffer tank to a minimum.
If the electrical load on the generator is below 25%, electrical heaters build into the buffer tank increase and hold the electrical load on the generator to the most efficient threshold for the specific generator type. That is especially important for diesel gensets, since they don't like running under-performed.
What kind of generators and fuel types are preferred :
Any liquid cooled Diesel, LPG (Propane) or Natural Gas generators can be converted into a mCHP system.
Alternative fuel types like Biodiesel, Veggie Oil, Hydrogen enhanced fuels and Wood Gas can be used with engine and control modifications.
How much energy output can be produced :
For example a 15kW diesel generator produces about 18kW/h (61,000Btu/hr) in heat at 75% (11kW) electrical load.
A typical run cycle takes somewhere between 4-5hrs. The thermal heat produced and stored during the run cycle is between 244,000 and 305,000Btu's in addition to the 40-50kWh on electricity produced at the same time.
The cost for fuel per kW (heat and power combined) is at 8 to 9 ct/kW for the above example, based on the fuel consumption of an Isuzu direct injected diesel generator.
We have built, tested and improved a demo 20kW (electric) / 123,000Btu (thermal) off-grid mCHP system, fueled by propane with a 2,000 liter Buffer Tank over the last two years and I would like to invite everybody who is interested in the combined heat and power technology to check it out at my shop here in Smithers. Micro-CHP's from European and Japanese manufacturers are not comparable to my design, since they are designed to run in Heat Mode only, selling the by-product power to the grid (Grid-Tie).
I would like to announce that we are ready for taking orders for custom build mCHP's now. Please contact us for more information and pricing.