How then, do we move backwards? How does a society, with most of the people having no clue of future events, move from being dependent on a vast and intertwined network of goods and services produced by the indigenous people of whereever, to a local resource and renewable energy based society, and do so in the timeframe available (20-30 years using the most liberal extimates, 10-20 with resonable estimates, 5-10 with worst case scenarios), all the while prices on everything increasing, world politics getting more militaristic, governments continuously reducing civil liberties, shortages of goods on the market and weather patterns resembling bad Hollywood movies?
A little bit pricey but it does the job in the desert where temps get up to 120F. Some people also convert an AC swamp cooler to DC using a 12v radiator fan to drive the air through the evaporative cooling pads.
Obviously HVAC is a major energy consumer, but my unit only draws about 85 watts. It would be nice if there were more energy efficient options in this area that could run off a small solar system. Geothermal with a heat pump might be worth experimenting with as well.
Joined: Aug 07, 2005 Posts: 302 Location: Columbia, MO
Posted: Sun May 18, 2008 4:04 am Post subject: Re: Anyone here know grid tie systems?
burtonridr wrote:
dooberheim wrote:
You can always wire two bulbs in series in a pinch.
Dk
Would that work on a 24v system?
Yes - 2 12 v bulbs in series require 24 V.
Here in Missouri we get an average of 4-5 hours/day of good sun. An 80 watt box fan does a reasonable job at ventilating the house. Even this, to use it 16 hours/day needs about 1.3 kWH, or the output of 300 watts of solar panels or so (more like 400, because of charging losses) and a couple of T-105 golf cart batteries.
Joined: Oct 16, 2004 Posts: 1365 Location: Appalachian Foothills of Virginia
Posted: Sun May 18, 2008 6:13 am Post subject: Re: Anyone here know grid tie systems?
burtonridr wrote:
skyemoor wrote:
It helps to chart out your eventual goal for your solar PV system. That way, you don't spend money on components that limit you or require spending much more to upgrade to larger components.
Do you eventually want to;
- Run most of you lights?
- Run your refrigerator?
- Power computers?
- Power a well pump?
- Other?
hmmm........
A refrigerator/freezer would be nice, my fear is that everything is falling apart much faster than I anticipated and I need to provide my family with the basics first. A lighting system is going to be essential, I prefer electrical lighting over candles or lanterns for safety and convenience.
I guess in the future I could always add the 120v system to run those things, and continue to use the 24v system for lighting.
Installing a 24v system independent from the 120v system would not limit a future 120v system.
What are your objectives? To be off-grid? Or to be net-metered and able to go off-grid if need be?
I'm currently powering my home in a net-metering arrangement with a 2 kW array and batteries. I can go off-grid if need be, but normally the batteries are on float and I spin the meter backwards when generating excess. The batteries are only used when there is a power outage, so their life is extended by at least a factor of 4.
Will you require running a refrigerator/freezer? If so, you need to choose between AC and DC and whatever your choice is it should require the least possible power. A DC refrigerator avoids inverter losses (and single point inverter failure) when under PV or battery power. Sunfrost is one brand, though there are others.
While the refrigerator is usually the largest energy draw in an off-grid home, a list of other electricity consuming devices needs to be drawn up with estimates of power usage (normal and emergency). Note that off-grid homes don't use heat pumps, A/C, or central HVAC at all, obtaining heat from passive solar and/or wood heat. There are a number of techniques to stay cool in the summer, though it helps to design most of them in before the building was constructed. Energy efficient landscaping is one that can be applied afterwards.
Joined: Dec 26, 2006 Posts: 241 Location: Eastern Washington
Posted: Tue May 20, 2008 1:45 am Post subject: Re: Anyone here know grid tie systems?
If there is power running to the site is there really anthing needed besides the small scale infrastructure required? _________________ "Those who long for exaltation look upwards, but I look downward for I am the exalted."
A little bit pricey but it does the job in the desert where temps get up to 120F. Some people also convert an AC swamp cooler to DC using a 12v radiator fan to drive the air through the evaporative cooling pads.
Obviously HVAC is a major energy consumer, but my unit only draws about 85 watts. It would be nice if there were more energy efficient options in this area that could run off a small solar system. Geothermal with a heat pump might be worth experimenting with as well.
I dont want to get off topic with this, however I want to answer your question quickly as well as point out some things you should think about.
First about the little unit you are using, without doing a cooling load calc on the living space you are using it to cool, I cant really tell you much. I'm sure it works, and actually it is probably less efficient than most units on the market. Most units are 80% or better on the efficiency aspect. Efficiency is the measure of how well something converts energy. There is a lot of technology built into other units, they use more electricity, there are more types of energy than electricity.
The page on the link says they recommend using it to cool a 300 sq ft room. Sometimes manufacturers will make a claim, but what they dont tell you is what kind of environment it is recommending or what it was tested in. If they tested it in a 300 sqft room, what was the wall insulation value? What was the roof insulation value? Floor insulation value? How many windows? If there are windows, which way do they face? south? north? Also what was the temperature difference between outside and inside the living space?
300 sqft is a whole lot of space to cool. If you have 10 ft ceilings thats 3,000 cubic feet of air you have to cool. Now that unit blows 1,200 cubic feet per minute. that means every 2.5 minutes you have circulated the air within the space. That is a lot of air movement for a single 300 sqft space... To give you an idea of just how much air that is, we typically use a unit that blows 1,200 cfm for about 900 sqft of office area.
Now you are somewhere that gets up to 120 degrees, just to cool the air down to 90 degrees is a temperature difference of 30 degrees.... So it will take a lot to cool that air down, off the top of my head I'm not about to figure it out.
But if, and this is a big if, that little unit cools the temp 30 degrees that would mean it is providing 3,600 buth of cooling.
Now another thing that units requires is a constant inflow of water. What is pumping that water to the unit? how many watts is it requiring? Can your solar system handle the load from the pump? Do you live near a reliable water source?
There really isnt any information provided on that website to provide more accurate numbers....
Anyway there are some things to think about, send me a PM if you have any other questions. _________________ Tired of high gas prices? Then stop driving to work, duh..... Learn to Work from home
Posted: Sun May 25, 2008 7:13 pm Post subject: Re: Anyone here know grid tie systems?
Something to keep in mind... Take a 15 amp 120vac typical outlet in your house... That gives you 1800 watts ( W=V*A ) so to run the same device on 12 volts, it will require 150 amps... Most houses are wired with #12 wire that can only handle 20 amps... Most houses only have a 100 to 200 amp service... This is why a higher voltage works better.
Also an incandecent light will work on 120vAC or 120vDC... An 120vac LED light will also work on 120vdc... 10 12V batteries in series and a transfer switch, and your wife wont know if its working on AC or DC... Many devices actually work off of DC without you knowing it...
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Then stop driving to work, duh..... 
