Solar Energy

[Nick1911]

Here is my latest scheme.  I've considered it for a long time, but the gas absorption cycle was too mysterious until the IcyBall device came to light.

Lets say I built a solar furnace.  A 4x4 sheet of plywood covered in mirror tiles with adjustable setscrews to control the angle.  The angle is set on each to focus on a central point.  A small (10 watt) photo voltaic panel runs a micro controller and stepper motors that allow the furnace to track the sun.

At the center, some type of liquid with a high boiling point (Oil? Antifreeze?) absorbs heat via a steel casing.  This oil is run back to the hot side of an absorption refrigeration system.  This is pumped at a slow rate via a VERY small pump that runs from the solar panel. For the refrigeration system, think similar in design to the icyball.  Instead of a metal sphere for the cool side, there is a grid like mechanism (think heater core).  At night, a small fan moves air through the cooling grid.  Ideally the fan would run from solar energy, but I don't think that's feasible.

Instant free solar powered Air Conditioning.  And, at a fraction of the cost of enough PV panels to run a regular window AC unit.

Issues: 
On a cloudy day, no AC 
Is it enough energy to cool a doghouse or a shop or a house?  IDK.
How hot does a solar furnace get?  We need at least 280F AFTER the losses in the oil-heat moving system
Ammonia is nasty stuff.  Safety is a concern.
Pressurized Ammonia is REALLY nasty stuff.  Use enough steel, and no brass!

Thoughts?

[280plus]

Coincidentally, I just read this:

http://online.wsj.com/article/SB119924708042261755.html?mod=yahoo_hs&ru=yahoo

So your idea is not without merit...

If you are familiar with the ammonia based heat pumps I installed, heating the ammonia with solar is not too far fetched at all. The tough part is getting the company to commit to the research.

[K Frame]

Don't you know that ANYTHING that attempts to reduce oil consumption or which smacks of a renewable energy source is EVIL, ANTI-AMERICAN CLAPTRAP?

I'm shocked, surprised, and dismayed.

[K Frame]

As for ammonia, you could always try methyl chloride or sulphur dioxide...

I think some of the early experimental systems also used ether... 

[Nick1911]

As for ammonia, you could always try methyl chloride or sulphur dioxide...

I think some of the early experimental systems also used ether... 

It would probably depend on what I could get my paws on if this project ever gets to that stage.  With the "OMG, Meth Lab!" knee-jerk reaction of todays world, anhydrous ammonia might not be real easy to come by.

Before any development to that end will occur, I'd have to build and test the solar furnace to make sure it can get hot enough, and can provide enough energy.  And before that could happen, I'd need somewhere to put a solar furnace.  My apartment complex isn't going to go for that.

An added bonus - with clever plumbing, in the winter you could use it for heat, providing everything was insulated well enough.

[ilbob]

On average, in North America, you will get somewhere between 3 and 9 kw/hr per day per square meter of solar energy. this includes cloudy days, and nights, etc.

a typical refridgerator uses something like 90 kwH per month, a really efficient one uses perhaps 15 kwh per month.

So your idea has some merit, however, heat cycle engines are not real efficient, perhaps 30% at best. and they work best at higher temperatures.

[Manedwolf]

I think "solar" will come when they make linkable solar panel tiles that look like regular roof shingles and cost the same as regular shingles.

Not till then.

[K Frame]

I think your biggest drawback will be with the solar furnace maintaining continuity with the sun. Oddly enough, it's not as easy as it sounds.

[280plus]

At least you're working on something constructive for a change... 

[Nick1911]

On average, in North America, you will get somewhere between 3 and 9 kw/hr per day per square meter of solar energy. this includes cloudy days, and nights, etc.

a typical refridgerator uses something like 90 kwH per month, a really efficient one uses perhaps 15 kwh per month.

That's very insteresting.  Thanks for the information!

So your idea has some merit, however, heat cycle engines are not real efficient, perhaps 30% at best. and they work best at higher temperatures.

That's true of heat engines, IE: the sterling cycle, but does this apply in a situation where heat energy isn't turned into mechanical energy?

I think your biggest drawback will be with the solar furnace maintaining continuity with the sun. Oddly enough, it's not as easy as it sounds.

Good point.  It's a "black box" I haven't figured out yet, but this page and this one looked promising.

[K Frame]

"a typical refridgerator uses something like 90 kwH per month, a really efficient one uses perhaps 15 kwh per month."

Exactly why I replaced my fridge a few months ago.

Damned thing was using almost 150 KwHr a month according to the door tag.

New one uses about 532 a year.

[ilbob]

Damned thing was using almost 150 KwHr a month according to the door tag.

New one uses about 532 a year.

Depending on your electricity costs, the upfront cost may never be recovered.

150 kWh per month = 1800/year. So you are using 1268 less kWh per year. At 10 cents/kWh that is just $125 per year.

[K Frame]

The replayment period for my fridge will be 4.7 years at current electric rates. I bought a very moderately priced fridge that has several more cubic feet of storage. I waited for it to go on sale, and then used an additional incentive to get it. I didn't run out and buy the biggest, flashiest thing I could lay my hands on so I could say I have a plasma tv on the door of my fridge.

The old one was nearly 30 years old and had to be replaced no matter what. The inside was starting to fall apart.

[drewtam]

Nick, how familiar are you with thermodynamics? Have you taken a college level engineering course?
It would serve you well to analyze your proposed system with such knowledge.

[Nick1911]

Nick, how familiar are you with thermodynamics? Have you taken a college level engineering course?
It would serve you well to analyze your proposed system with such knowledge.

Unfortunately, I graduated college without taking such a course.

[drewtam]

Issues: 
On a cloudy day, no AC 
Is it enough energy to cool a doghouse or a shop or a house?  IDK.
How hot does a solar furnace get?  We need at least 280F AFTER the losses in the oil-heat moving system
Ammonia is nasty stuff.  Safety is a concern.
Pressurized Ammonia is REALLY nasty stuff.  Use enough steel, and no brass!

Thoughts?

You can solve the cloudy day issue by supplementing the heat with natural gas. Or have a back up AC system. If there is an AC system already installed, that would be cheapest/best option since its already installed (sunk cost).

The cooling capacity of your system depends entirely on the variables: the size of the solar collector, the size of the heat exchangers, etc. The best option would to contract a mechanical engineer. I expect established firms would charge about $100-$150/hr to do your analysis. I would probably charge $50/hr + travel. I would expect that a site visit would be required for a rough concept. It would likely take about 10-20hrs worth of work; and would not include any site planning or design (just conceptual work). The deliverables would be  project scoping and rough estimates of performance and project cost. From the project cost, one can perform the economic analysis of whether the whole thing is worth the effort.

For example it might save $200/mo in the summer from cooling costs - yay! But it costs $40,000 to install, and summers only last 3mos/yr, so it would be decades before a ROI was realised -bummer. The system would decay before ROI was provided (much like hybrid cars).

[280plus]

Turns out, Robur is actually working on an absorption cooler that uses hot water to heat the generator...