Open Project to Develop Renewable Energy System

rohar writes "We have been working on a system that combines some existing indirect solar technologies to build a location independent, renewable, reliable and economically feasible indirect solar electrical power generation system. The idea is to 'roll-your-own' geothermal source by capturing heat from the ambient air with a solar powered absorption heat pump, store it underground and generate electricity from the air cooling convection. When the air is cooler the stored heat is then used in a reverse process to generate electricity by transferring the heat back to the air when it is cooler (at night or seasonal). There are many additional benefits including clean water capture from the "dehumidifier" effect of the air cooling, construction from common materials and thermal storage that may be incorporated into dwelling heat systems." After reading over their description, how likely do you think it is to work?

Wind turbine

[Technician]

After looking at the diagram, it is evident the math is not done. A few things come to mind. The most glaring is the wind turbine. Anybody you know of put a turbine in the fireplace flue to get electricity from the heat draft? This is a draft with a large heat change. How much draft do you expect to get from the day/night differential. Don't expect enough juice to power the water pump in a water cooled PC.

Getting the heat to provide the high pressure ammonia to feed the expansion valve is also a problem. Time to do the math.

A good place to start is Modern Refrigeration and Air Conditioning.
http://www.bizrate.com/technologybooks/modern-refr igeration-and-air-conditioning--pid4254146/ [bizrate.com]

Instead of trying to get high pressure ammonia, look up continious cycle absorption cycle refrigeration. The key is using vapor pressure to your advantage. Day/night cycles are not going to provide the requried amount of pressurised liquid ammonia for the job.

Study and learn continious cycle absorption cycle refrigeration then redesign and eliminate the expansion valve, & turbine. Add a light weight inhert gas to the entire system to make distilation of ammonia possible and stop uncontrolled reasorption into water.

Probably going to need active cooling

[Anonymous Coward]

After skimming over the design, my gut tells me that the system is also going to need an active cooling component. For the steam turbine to operate efficiently, he's going to need to cool the working fluid below its boiling point. Otherwise a lot of energy is wasted pumping the working fluid in its gaseous form. To operate continuously without an active cooling system, the cold reservoir will need to always be below the boiling point of the working fluid. Now this works in the winter when the air cools off and the system is using air as its cold reservoir. But since he's transferring heat from the ground, we must assume that the ground is above the boiling point of the working fluid. Therefore he runs into the problem that the ground won't cool the the working fluid below its boiling point when the system is operating in reverse, with the ground as the cold reservoir and the air as the warm reservoir. As a result, he'll need to either replace the working fluid when the system starts using the ground as the cold reservoir or integrate an active cooling system.

Re:So...

[noigmn]

Their idea was storage using heat pumps so you can use the energy at night rather than use battery storage. It wasn't claiming a new form of power production.

As for production of energy if they wanted to not store it then ground/air temperature difference during the day would probably be similar to day/night air temperature difference.

Re:So...

[Sub Zero 992]

Drilling deep holes can cause earthquakes:

http://www.swissinfo.org/eng/front/detail/Geotherm al_project_shakes_Basel_again.html?siteSect=105&si d=7407138&cKey=1168104002000 [swissinfo.org]

Not Yet.

[WindBourne]

Isn't the most viable alternative energy available today solar PV cells? Already proven technology and now even affordable!

At this time, Solar provides the least amount of energy of all of the alternative systems. Hydro, wind, geothermal, and methane generation currently provide more energy than does solar. In addition, they do it cheaper.

But long term, homes will probably be better off using a geothermal heating/cooling combined with electricity from pv systems

Rough efficiency

[clare-ents]

Assuming a hot temperature of 70C (black plate in strong sunshine) and a cold temperature of 20C, the theoretical efficiency limit is (343-293) / 343 or 14.6% - assuming a perfectly efficient generator and a very large capacity foe the 85% waste heat capacity.

At night, it's going to be more like 30C -> 0C which is down at 9.9% efficiency.

Even cheap solar cells do better than that, you'd be better off just buying solar cells.

It is a solved problem

[IMustBeNewHere]

I don't know about the part of his design that is above ground.

The underground bit however, works well in practice, at least in the Swedish climate.

Extracting heat from a temperature differential with a heat pump and storing it in the ground, is in wide commercial use here, and you can save money on it.

In a quick search in the Swedish yellow pages, I found hundreds of contractors to choose from.

There has also been plenty of research conducted in this field in various Swedish universities. The article author would probably save himself a lot of time if he looked some of it up. Here are a couple of abstracts (in English and Swedish):
http://www.lib.kth.se/main/stems_projektrapporter. asp?subj=vp [lib.kth.se]

Re:The analogy to Linux

[Anonymous Coward]

The analogy to F/OSS has been applied quite nicely to architecture http://www.architectureforhumanity.org/ [architectu...manity.org] hardware http://en.wikipedia.org/wiki/Open_source_hardware [wikipedia.org] .

The absence of capital does not seem to be a prerequisite for the success or usefulness of this model.

Re:hmmm

[tacocat]

Effectively speaking, you can't store heat in the ground. If you could, then heat pumps today wouldn't work. And plumbing in the north would fail every year. The ground temperature much below 3-6 feet stays a relatively constant temparature all year round. I think between February and August it might vary 10F if that.

The point being that if it takes 6 months of weather on the surface to effect a 10F change in the ground, you won't be able to create a heat pump powerful enough to make this project work. The earth has the property of being a massive heat sink with a reasonable thermal conductivity. This allows heat pumps to pull heat out of the ground in winter and push it into your house. They become inefficient at very low temperatures because the heat transfer freons don't work very well, not because the ground runs out of heat.

It might be more possible to do this if you had an insulated/isolated storage of water and used that as the heat source for storage and retrieval. You could also do it with air and stone. But in every case, you have to provide a means of thermal isolation between the earth and the storage facility. Also, it would be far more efficient to store the heat by means of thermal exchange pipes (solar heated pools) than trying to pump the heat into place.

The convection tower concept isn't new. I think someone came up with that in Australia about five years back. But the storage of heat for later retrieval is.

Re:Wind turbine

[Technician]

OK - I have not read the article but I will point out that a century old kerosene refrigerator uses a wick and not a great deal of fuel plus a bucked of water to handle expansion and condensation.

Early kerosene refrigerators used a single cycle sytem where the ammonia boiled or evaporated as it was absorbed into water. To get the ammonia back and the water, the cold side was stuck in the bucket of water and the room temprature water chamber was heated by the kerosene flame to seperate the ammonia from the water. Do a Google search on "iceballs ammonia" for a version that still entertain people today who build their own.
Before you build your own, remember this runs on high pressure during regeneration, and uses ammonia, a relatively hazardous material.

http://www.ggw.org/~cac/IcyBall/crosley_icyball.ht ml [ggw.org]

Simple day/night tempratures will not complete the regeneration cycle. The temprature is too low. Even though very little kerosene is burned in those refrigerators, the burning kerosene did provide the required tempratures to complete the regeneration cycle.

Re:hmmm

[rohar]

Drake Landing Solar Community [www.dlsc.ca] is an example of seasonal thermal storage.

bought a corn stove

[codepunk]

I got real pissed off last year and decided that I am no longer gonna be subjected to
swings in the fuel market. I bought a corn stove and installed it, best thing I ever did, so far
this year heat has cost me less than 1/3 of what it normally does. Much simpler system than what is described here, corn in and heat out. My stove is also multi fuel if corn goes high I can buy wood pellets, barley, cherry pits etc whatever is running the cheapest.

Re:Call me prejudiced, but...

[wintermutex]

To be fair, "roll your own" is not pot-smoker slang, it refers to rolling your own tobacco cigarettes in lieu of buying packaged pre-rolled cigs. It's a lot cheaper and sure, could be seen as 'pot chic' to do, but the term's been around about as long as cigarettes have been manufactured.