What does power mean? Or, more #@%* math

Many times when I describe how much power a solar array makes, the common question is "just what does that mean, how can I relate to the amount of power produced?"
When talking about power, there are two basic types of power measurement. One is the solar array rating and the other is what it makes over time.
The array rating is usually stated as watts under Standard Test Conditions or STC. These conditions are shining 1000watts of light energy onto one square meter at 25 degrees Celsius. When PV modules are made, the manufacturer "flashes" this amount of energy upon the module being tested. If it falls within tolerance, it passes the test and is labeled as so many watts STC.
The rating therefore is an instantaneous reading of energy output. It really hasn't done any work, since it takes power over time to arrive at an understandable unit of work or power.
Common output instantaneous ratings are described as:
Watt (W, after James Watt, inventor of the steam engine and definition of horsepower)
Kilowatts (KW; 1000 watts)
Megawatts (MW; 1,000,000 watts, 1000KW)
Gigawatts (GW; 1,000,000,000 watts, 1,000,000KW, 1000MW)
and so on.
When describing practical power, you must add the element of time. On average, on a SE West Virginia Summer day, you can expect 5.2 peak sun-hours per day. This unit goes back to the STC thing, 1000 watts per square meter. This is how we quantify solar energy through the seasons with all the clouds, rain, snow, and shorter days thrown in.
So, say you have an array rated at 2000 watts STC on a 5.2 peak sun-hour day. simply multiply 5.2 x 2000 and to get 10,400 watt-hours or 10.4 Kilowatt-hours for the day.
Now, we have something to grab on to, a quantity of useful, practical power.
So, what the hell does a kilowatt-hour mean to ME? Its surprising in this day and age that we are so used to having so much energy at our fingertips. Why, I remember in the old days, (not really) how little power was available to us. Back in days of yore, we had muscle power (human and animal), water and wind power to accomplish our work.
If you had a 1 horsepower electric motor, it would take about 1 kilowatt of electricity to run it. A horsepower is actually 746 watts, but with inefficiencies, it takes about a thousand watts. OK, so a Kilowatt-hour is worth one horsepower-hour, so what? When James Watt experimented with rating horsepower, he used big ol' draft horses, working at peak power over short time frames. When I say peak, the horse was working at levels that were not sustainable. I'm sure you are starting to get a handle on this power.
For you geeks, I'll explain what a horsepower is worth: it is 33,000 ft-lbs per minute. In other words, a horse could lift 33, 000 pounds a distance of one foot in one minute. Conversely, it could also lift one pound, 33,000 feet in one minute or any combination between. That's a bunch of work! In WV, we pay about 9 cents worth of electricity to do the same work. No wonder we have become so detached from the understanding of power and how cheap (artificially) it is.
So, back to the quantity of power from a 2000 watt array. Over the course of a Summer month, you could expect 312 KWh to be produced. You must subtract some power loss from inefficiencies of the inverter, line losses, and the fact that Summer heat reduces output compared to the STC rating. By observation, I determined the Summer efficiency rate of 90-92% for a complete high quality PV system, so my guess you would net 290 KWh.
What are the energy equivalents of that 290 KWh? You could do one the following activities:
>You could run your toaster for 8 days straight and make 4640 slices of toast
>The Budweiser Clydesdale hitch could pull a fully loaded beer wagon, up grade, for 48 hours straight.
>You could vacuum your house for 232 hours straight or 9.6 days, whew!
>Heat 2000 gallons of water from 60 to 120 degrees F.
>Run a large room air conditioner for 6 days, around the clock.
>Drive your car at 40 MPH on a level road for 19 hours and go 773 miles.
>Burn 8 CFL lamps rated at 100 watts of light (23w actual) for 65 days.
> Watch TV (LCD type) around the clock for 80 days, snacks not included.
Now let's look at what the equivalents are when you throw the switch:
>You turn on 4 CFL lamps- a healthy person works at maximum power for a while and the lights go dim as he becomes exhausted.
>Toast a bagel- A large draft horse pulls all it can for about 5 minutes.
>Turn on the room AC-A team of 2 to4 draft horses pull all they can for as long as the AC is on.
>Turn on all electric heat- Your 24hp lawn tractor runs at full bore mowing tall wet weeds.
I hope all this helps you to form some mental images as you go about living and realize how plush we have it, for now.

Bigtime

July 24, 2010. Mountain Messenger newspaper. Lewisburg, WV

West Virginia Enters New Age

Although WV has had net metering provisions they haven't been very good compared to other states. Recently, a new set of rules have been passed by the PSC to put WV's net metering among the best in the country. I am so happy this happened without too much dilution from the powers that be.
Read all about it at http://irecusa.org/2010/07/july-2010-connecting-to-the-grid-newsletter/
Download PDF at bottom of page then go to page 3 to read all about it.
Yeah!

Climate Change Fix

I have no idea how many people read my blog. Other than the occasional comment, there is no counter of visitors to gauge the readership. I hope this blog can be an effective tool to plant some ideas that can help raise the awareness of important issues.
My usual M.O. is to approach softly and supply facts and figures to support an issue. Sometimes it's subtle promotion of concepts, our solar business, or myself. I read an article why people Twitter, YouTube, camgirl, and blog. If there is some sort of audience, it validates your existence. Sometimes the only audience is one's self. Same effect.
The topic covered in this post is global warming. Actually, it needs to be referred to as climate change. We watch the news and are aware of our surroundings. Things are happening to the planet in increasing frequency and intensity. Take last winter for example, I haven't seen a Winter like that since 1976-77 back in Pennsylvania. The cold and snow were caused by El Nino...the WARMING of equatorial waters in the Pacific. Then, in late Winter we went to late Spring weather just like that. Early in July NOAA reported that June was the hottest...ever. July itself is not far behind. I can't remember how many times the temp was over 90, but I cannot recall such a streak in the 32 years I've been here in the high country of WV.
Think hard, how long has it been since you thought some particular season was normal? Isn't every season some sort of a surprise? One can go for years and not realize the accumulation of evidence. I have noticed an increase of poison ivy, and for the first time, found termites. What's next Kudzu? These are signs of a warming West Virginia. They say in a hundred years WV will be a high desert, like in New Mexico.
Headlines abound; 520 Belgians die in heatwave, Argentina braces for severe cold, floods in China and the US midwest. On and on and on. Was the news always like that? Is this Al Gore's doing?
Climate change will effect our clean energy capacity. Right behind the energy crisis is a critical water crisis. As drought deepens in certain areas, the hydroelectric dams are diminishing in output. Not only drought lowers the water levels, but irrigation of the desert takes a huge amount of water. Our current thermoelectric power plants consume and evaporate a tremendous amount of water. What if there is not enough water where and when needed?
CLEAN COAL, Ha! In order to capture the CO2 emissions it will require doubling the water use. How can anyone put up a billboard near Charleston, WV that says COAL...CARBON NEUTRAL. Trees are carbon neutral, not coal. What some groups get away with.
The Earth may have something up her sleeve. If the Greenland ice cap melts off, there is enough fresh water to stop the equatorial conveyor currents from flowing. The result is irreversible, an Ice Age will begin, not over hundreds of years, but within a decade of the currents stopping. That will sure take care of the issues, huh?

Let's Talk Diesel

More than once someone said "I won't have a diesel because diesel fuel costs more than gasoline". I think; geez, I won't comment to this dude on that. But, then I wondered just how much more economical is a diesel? You see on TV how train locomotives haul one ton of freight 400-some miles on a gallon of diesel. And those big rigs on the road weighing 80,000 pounds getting 4 MPG. Could you imagine if those trucks were burning gasoline? one or two MPG?? Or, maybe how many gallons per mile?
Let's do some really fun math......
We'll compare a 3000 pound sedan running on gas and getting 36 MPG on the highway against the previous generation WV Jetta TDI diesel, also weighing in at 3000 pounds. Fair enough?
The Jetta gets over 50 MPG on the highway. In fact, we measured 54 MPG on a trip to Boston and back. Another trip we documented was at 52 MPG.
As of today the national average price of gas and diesel was $2.71 and $2.90 per gallon respectively. Gasoline has a heat value of 114,100 BTU/gal and diesel 130,500 BTU/gal. That's 14% more energy at only 7% more cost.
But there's more. A modern gasoline engine is 30% efficient, while a diesel is 40% efficient. Both efficiencies are rated at highway speeds in overdrive or 5th gear. Now, if we take those BTU/gal values and multiply out at .3 and .4 we get 34,230 BTU gal on gas and 52,200 BTU/gal for diesel. This is the amount of heat turned into work by the engines. The rest of the heat goes out the cooling and exhaust systems. The diesel delivers 50% more work than the gas engine.
Let's look at the MPG figures again, 36 for gas, 54 for diesel. Amazing, 50% better mileage.
What does that mean economically? For every gallon we burn in the diesel we go 18 more miles down the road than on gas. This equates to $0.95 saved per gallon. We paid $8000 for our used Jetta, can you figure out how many highway miles we would have to travel to pay for this vehicle?
Of course, there is the issue of pollution. A diesel is dirtier than a gas engine. (except the lastest generation of clean diesels) But, the pollutant outputs are measured per mile driven. More mileage, less pollutants per mile. If you add only 2-5% biodiesel, you sweeten the exhaust and is the best anti-wear additive there is. If this prevents your engine from wearing out sooner, just how green is it to prevent building another engine to replace it?
Americans don't like diesels like Asian and European countries. That why the selection is quite limited in the states. Most diesels are found in 3/4 ton and up pickups, few sedans.
When we drive down the highway, I can go a hundred miles before seeing another car that matches our mileage. Feels good, I get a little smug. Even a Prius can't catch us, except in the city, where it benefits from regeneration of electricity from braking.

More about the pond

Putting in the solar aeration system keeps me thinking more about the pond itself. We constructed the pond back in 1988 at the site of 2 conjoined sinks. With a little dozer action and managing to seal the basins, I had a receptacle for water to fill. The pond has 1.5 acres of surface, about 14 feet deep, and holds about 4 million gallons of water. Once full, it was barren. So I hauled in buckets of water and muck from surrounding natural wet places and streams. This I hoped would seed the water with all the lower life forms to support higher fish and animals.
After a while I stocked both small prey and smallish predatory fish. Over time I stocked minnows, blue gills, channel catfish, large mouth bass, and a few species caught in the Greenbrier river. All was going well except for the few Northern Pike I put in. I had to remove them because they ate EVERYTHING that moved.
After a couple years, I noticed cattails growing. At first I freaked out, surely they will overrun the place and will not match my image of the perfect pond (human version) It took a little while but I realized they could not grow in the deep part and by now would be a monumental task to remove them.
Then one Spring some Red Wing Blackbirds showed up and they stayed to nest. Apparently they prefer last year's dead cattails to build their nests. They are a joy to have around with their song and antics. Swifts and Swallows also came to nest nearby and show off their superb flying skills skimming bugs off the water in dive bomb raids. While that was happening bats flew high above them eating more insects. They live in our caves but come to the pond to eat. I suppose that is why we have only 3 or 4 mosquitoes a year that bug us.
Since then the pond is now used as a layover during migrations, we've identified a swan, black ducks, loons, buffleheads, wood ducks, mallards, geese, and some water fowl we're just not sure of. We also get visits by green and blue herons, osprey, and egrets. I believe they live on the river and come up to fish.
Soon I discovered mussel shells on the banks along with coon tracks. I wonder how the mussels would taste, so far, I don't know.
Animals come to drink like deer, coyotes, possum, and last week a fairly stout black bear during the dry spell.
Maybe this will be the best thing I ever did for the planet. Its certainly equal to the 70 acres of recovering future woodlands I have. Before there was just cows farting methane and a few species of grass and weeds. Now there is the habitat to support a very rich biodiversity that could otherwise not happen except for the pond. Making a small carbon footprint is to be encouraged, but actually adding something to the earth is the most satisfying thing one could do.

Alterra PV on Web

The final step in our home gridtie system is finally in place. The data from our microinverters and PV system is available nearly live on a website. The microinverter manufacturer provides this service at little cost and we can access at anytime. The data will accumulate for years to come and help to diagnose and see if we are hitting our yield targets. I invite you all take a look with a special visitor's pass:
http://enlighten.enphaseenergy.com/public/systems/GAMW5313
Be patient for all the data to load
Thanks