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Talk:OS:Sterling Allan's Sustainable Home

Lasted edited by Andrew Munsey, updated on June 15, 2016 at 1:59 am.

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Stirling Engine backup

On Nov. 3, 2009, Vincent Howell wrote:

So what type of heating will you have Sterling? Gas, wood/pellet stove, fireplace, or central heating?

If he chooses a fireplace or a wood/biomass stove then I believe I have an idea for a completely off-grid power solution without the need for a gas generator. So lets assume Sterling chooses an off-grid solar power system with battery storage for night operation. Great, but what about during the cloudy, rainy or snowy days, when solar is inadequate (unless the 10x power concept is adopted)?

What if the fireplace or stove was modified to accommodate part of a stirling engine (the hot part)? The same source that heats the home can also run a stirling engine which can then power a generator that charges the battery banks in the solar array. The stirling engine should use compressed nitrogen or helium and have a regenerator to increase efficiency. The ideal solution would be to replace the air with liquid nitrogen then allow the liquid to phase change into high-pressure nitrogen gas inside the engine. A stirling engine will have improved power output with a preasurized gas and nitrogen is a good choice because the oxygen in compressed air can cause an explosion if it comes in contact with the hot piston and any lubricating oil.

The stirling engine can be water-cooled with water re-circulated through a radiator & fan assembly then stored in a warm water tank to be pumped back to the cold side of the engine. The water tank will serve an additional purpose as the homes hot water heater. The water is heated as it flows through the engine. With the proper engine radiator and water filtration system, the resulting hot water will be perfect temperature for shower and other uses. Auxiliary power for the water heater tank can come from solar thermal heating (coils of black hose/pipe on the roof with water circulated through it during hot sunny days). The water used would be replenished by the city tap or well like a normal water heater. In fact, I see no reason why a typical water heater tank couldn't be used just don't connect the power.

So there you have it... an unusual means of renewable yet reliable power--a solar & stirling engine hybrid with the possible expansion for a wind turbine. Heating the home is necessary here during the early-spring, fall, and winter months (unless I want to freeze) so utilizing that heat to generate power that can keep the battery bank charged and provide hot water is a smart move. During the summer months, hot water can be provided by the coiled hose on the roof.

Of course a gas generator would be less expensive and simpler but that is far too conventional for such an unconventional home after all the house will be constructed from bags of dirt and concrete.

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If you're really serious about your interest in a solar power system with stove/furnace-tied stirling engine backup then this might be a good book for DIY ideas:

You'll notice that a stirling engine is larger for the same power of gas engine but power-to-weight ratios can be improved with pressurized gas--my suggestion is to pour liquid nitrogen inside the engine, allowing it to expand 700 times into high-pressure nitrogen gas the gas would then be the sealed working fluid. 5 HP is more than enough for the average home with the sole purpose of running a generator to charge a solar battery bank. 1 to 3 HP would be enough IMO.

Still... solar power with stirling engine backup won't be cost effective for powering any 220V appliances, such as your washing machine or dryer. What is your plan of action for this?

Perhaps a natural gas washer and dryer?