Your Questions About Sustainable Energy Systems

admin answers:

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A few things:

Running your entire house from solar panels requires a massive installation and battery storage for those times when there is no sun (night, rain, snow, whatever). Effectively, the installation will need to be at least three times larger than the house peak load. If you have a small house and few electrical requirements that is one thing. But if you cook, heat, cool and make hot water with electricity that is entirely something else.

The typical solar panel gives very roughly 15 watts per square foot (150w/square meter), so you would calculate the amount of power you need at peak load (water heater + stove + heat), derive the number of square feet to make that peak, multiply it times three and you would have the area required. If you can control and limit your load at some arbitrary level, use that.

So, assume that you want to be able to heat or cool and cook at the same time, run a refrigerator, have some light, but you can restrict your hot water use and other appliance use to times when you are not cooking. A stove will use about 8800 watts of power. A refrigerator will use about 800 watts. Heating/cooling in say…. Six rooms in a moderate climate will use about 18,000 watts.
800 + 18,000 + 8,800 = 27,600. Divide that by 15. That comes to 1840 square feet. Multiply that times three – that comes to 5,520 square feet of solar cells in order to create a self-sustaining system. That is the equivalent of a square 75 feet on a side.

The average cost per watt for solar power is about $4 – that is without any credits or subsidies. And you will have to add inverters and battery storage as well as the infrastructure. So, your cost for the installation will exceed US$100,000 – actually it will be very close to $150,000 when all is said and done. Deduct any credits and subsidies applicable for your final cost.

Our average power bill in Pennsylvania in an unregulated environment runs to about $140/month, or $1680/year. That works out to a payback at around 89 years – well past the expected service-life of the panels. With available subsidies and legislation pending in Harrisburg, that may be reduced to about a 25 year payback – about the life of the panels. And we would cover the entire roof + half of the rest of the property. Just not practical if the goal is to be off the grid.

admin answers:

To be able to calculate the drop in sea levels you would need to know the mass of hydrogen that would produce the energy required. From that you could work out the weight of water that would need to be electrolised. Ignoring heavy hydrogen, this would be if my memory serves me 5 times the weight of the hydrogen. Two hydrogen (atomic weight 1) one oxygen (atomic weight eight). All you need then is the surface area of the oceans. One cubic metre of water weighs a metric tonne approximately.

Considering the ratio between surface areas of ocean and land.
I’m guessing that the area of land required to store the hydrogen extracted from just a metre of ocean would be huge.

I wonder why we would want to store a years worth. To be sustainable we would have to be able to generate the same amount as we use. Without that capacity eventually any reserves would become depleted. The only extra that would be needed would be a small buffer to cover disruption in supply and the amount in transit from generation plant to distribution points.

On that point your question stated a usage of 10^17 kJ. Is that daily, weekly or annually?

Thanks for a really interesting question.