Solar panel question?

[iconoclastNYC]

I made a rough estimate of what it would take to replace the energy my building uses from electricity from the local utility (at 20 cents per kilowatt hour) and fuel oil (2.27/gallon.)

I estimated that I need 100,000 kilowatt hours of generation per year.

If each solar unit produces is rated at 300 watts how many would i need to generate my needs?

I can't figure out the math.

Also how would i figure in cloudy days.... i'd need to overbuild to ensure peak loads are met, right?

[JohnWxy]

1. First of all you're going to have to find out how much solar energy

on average falls on your site. If you live in Seattle Washington, you might want to forget it, or get a very large, flat (one story) building. :-)

[iconoclastNYC]

2. I'm in NYC

And the roof is flat.

Here is a great document that discusses solar potential in NYC

http://www.powernaturally.org/Programs/pdfs_docs/10_Solar_NY.pdf

[phantom power]

3. As an estimate, solar panels operate at about 25% rated capacity.

In other words, the total amount of energy they produce over an entire year, smoothing out day/night cycles, seasonal sun changes, weather, etc.

A 300 watt panel produces an "effective" 75 watts, if you want to multiply by the number of seconds in a year.

However, that 25% figure is an estimate, and reality will depend on your lighting/shadow conditions, lattitude, weather, etc.

[seriousstan]

4. You will get about 2-2.5 peak sun hours a day or about 2000 Whr/sq in

Gotta go, I'll finish the calculations later.

[madrchsod]

5. it`s going to cost a bundle of money....big bundle

check around for alternative energy sources and conservation in nyc. i don`t have my design magazines handy but there are tons of resources on making buildings more green and efficient.

[iconoclastNYC]

6. I know it's goign to cost lots of money

But if we're talking about saving $40,000 a year in electricity then it might be economically possible. The new concentrating solar tracking systems are quoting 8 year ROI, and electricity produced at 9cents a kilowatt hour. We pay very high rates here in NYC for home heating oil and electricity.

I read somewhere you get a 30% tax rebate for new solar installations.

[Dead_Parrot]

7. Well...

Assuming the 300 watt rating is the capacity (i.e. electricity produced when the sun's shining) and you get a minimun of 4 hours a day decent sunlight...

100,000,000 Wh/year = 273,972 wh/day: divided by 4 hours, you'd need 68,293 watts of capacity, or ~230 modules. You'd also need storage for ~238 KWh.

You might want to consider leaving the heating seperate, since solar's not really suited to that (great for A/C, though) :)

If you go days on end overcast (which I imagine you do) I'd suggest leaving the thing grid connected so you can tap into it if needed, or the storage costs will be insane. Edit: You could also look at selling exess to the grid in summer, to off-set the costs.

[jpak]

9. NY has a net metering law - no need for storage...

n/t

[Dead_Parrot]

10. Got a link? might be useful info... nt

[skids]

8. Replace the oil with solar heat units, not electrical.

They are much less expensive per "watt." They are also a good starter project.

Also before you look at putting up PV make sure you've done what you can to reduce your electricity use (CF bulbs, newer appliances.)

You can work out rough estimates here: http://findsolar.com

[jpak]

11. rough estimate

For 100,000 kWh per year, assuming 3 hours of peak sun a day, you will need a ~100 kW system (which is a really BIG system).

With all the whistles and bells required for a net metered system, this will cost you ~$1 million BEFORE any state or federal tax credits or rebate.

The current federal solar tax credit for businesses is 30% of the cost of the system. Which might bring the cost down to ~$700k.

I'm not sure what NY has for solar rebates, but I believe they are ~$3-5 per watt depending on the size of the system. Assuming $4 per watt, that would bring the total cost (after fed credits) to ~$260k, or about ~$13k per year over the 20 warranty period of the PV panels.

At 20 cents per kWh you would spend ~$20k per year to by electricity from the grid.

So it might save you ~$7k per year with PV (assuming your rates don't go up over the next 20 years - lol).

If you are serious about this, you should contact a local solar installer/contractor and have them run the real numbers for you..

[oldhippie]

12. It'll take some area....

100 KW array with 300 watt panels running about 12.3 W/sqft equals about 8130 square feet of solar panels. Gonna need a good size roof.

Oh yeah, did we mention hail? And birds? Someone has to go up and clean all the bird poop off the solar panels periodically. I do mine, and it's a PITA. :)

[happyslug]

13. Have you thought about Non-electrical Solar Panels?

For example Hot water solar panels. I see you are in New York City and thus endure sub-freezing temperatures, but that does NOT mean you can NOT have hot water solar panel. There are three ways to handle the affect of sub-freezing water, first you can insulate the panel and install electrical heaters to keep them above Freezing, Second you can drain them whenever temperature drop below 32 Degrees Fahrenheit, or third you can use a glycerin material instead of water.

The general Consensus is that if you have more than a few days of Sub-freezing temperatures (Anyplace north of the South, the Southwest or Southern California) the best option is to use Glycerin. The glycerin freezing at temperatures while below freezing so you can keep the solar water heating panel in use even in winter. Unlike true solar water heating panels which heats the water directly, in a glycerin system the glycerin is heated in the panels, then runs to an inside water tank. The hot glycerin heats up the water, both cooling the Glycerin and heating the water. The glycerin is then run back through the panels and the whole system works again. As to the water, the hot water is used in the house and cold water is entered into the tank. Do to fact that the solar system does not work at night a cutoff is often installed to bypass the solar water tank when the water temperature in the tank drops below a certain temperature (Or in the alternative another means of heating the water in the water tank is used as an alternative heating system).

Solar hot water systems are more cost effective than Solar electrical panels. First heating water is one of the highest costs in any home, second since you are dealing with glass heating a liquid (either water or Glycerin) it is very efficient compared to electrical system. This is the preferred solar system for over 50 years in parts of Florida and other areas with no access to Natural Gas and high Electrical bill (electric heating of water is extremely inefficient and costly).

My point is you may be better off installing a solar hot water system (using a Glycerin instead of water do to the fact you are in NYC) than an electrical solar panel system. The initial costs will be higher (Running water pipes up to the panel, and back down to the glycerin - Hot water exchange), but the return on investment do to lower hot water heating costs is greater.