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Solar Energy Forum I have no doubt that we will be successful in harnessing the sun's energy.... If sunbeams were weapons of war, we would have had solar energy centuries ago. ~Sir George Porter

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Old 2nd-February-2007, 06:36 PM
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Default PV output considerations on overcast days -- some questions.

Today, it's bright out here in Maine, but overcast -- no bright sun shines.

What happens to a large array of PV cells on a day like this?

I am keeping a log all the days when we have bright sun here. I'm going to use this data along with my electricity usage information to try to sensibly design a PV-inverter-battery storage system.
Can I expect to draw any energy on a cloudy day, and overcast day?

Will it be necessary to build a small prototype to measure voltage outputs, relative to the "sunniness"?

If I can expect anything from my solar array on days like this, how long can one expect to be able to draw off one's battery banks?

Lots of questions, I know. I'm just starting this thing, any input from experienced folks is very appreciated.

-- Phil
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Old 3rd-February-2007, 11:52 AM
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I think I've read somewhere that they can still produce energy when it's not sunny although hopefully someone that knows more than me can answer with more authority
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Old 3rd-February-2007, 11:53 AM
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This seems to be quite a good article on how they work. Might be worth reading

http://www.thesolarplan.com/articles...nels-work.html
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Old 21st-February-2007, 08:26 AM
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My company recently began carying solar panels for telecommunications installations. Our first installation has worked quite well and has become our test case for calculations of larger installs.
Solar panels generate electricity by converting photons into electrical energy. Photons are available in all visible light conditions. Direct sunlight is desirable for "optimum" conditions, but any light level will produce some power.
If you construct your system properly you will design around the battery power first, then the solar second. I design our systems based on uptime in the dark. This is easy when your power draw is real low. For an average house, your going to need a load of batteries. Figure your total draw over an average day and night, then calculate your average amp hours. Once you have your draw, then you can figure how many batteries will be needed to provide one day, 12 hrs, whatever you will consider your minimum requirements. Now you can add the cells for charging.
Make sure you have lots of low draw appliances, and all the usual energy saving stuff.
I hope this is correct and helpfull. Look on line for solar or battery calculators for more help.
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Old 22nd-February-2007, 03:08 PM
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Default MANDATORY RENEWABLE ENERGY – THE ENERGY EVOLUTION –R13

MANDATORY RENEWABLE ENERGY – THE ENERGY EVOLUTION –R13

In order to insure energy and economic independence as well as better economic growth without being blackmailed by foreign countries, our country, the United States of America’s Utilization of Energy Sources must change.
"Energy drives our entire economy.” We must protect it. "Let's face it, without energy the whole economy and economic society we have set up would come to a halt. So you want to have control over such an important resource that you need for your society and your economy." The American way of life is not negotiable.
Our continued dependence on fossil fuels could and will lead to catastrophic consequences.

The federal, state and local government should implement a mandatory renewable energy installation program for residential and commercial property on new construction and remodeling projects with the use of energy efficient material, mechanical systems, appliances, lighting, retrofits etc. The source of energy must be by renewable energy such as Solar-Photovoltaic, Geothermal, Wind, Biofuels, Ocean-Tidal, Hydrogen-Fuel Cell etc. This includes the utilizing of water from lakes, rivers and oceans to circulate in cooling towers to produce air conditioning and the utilization of proper landscaping to reduce energy consumption. (Sales tax on renewable energy products and energy efficiency should be reduced or eliminated)

The implementation of mandatory renewable energy could be done on a gradual scale over the next 10 years. At the end of the 10 year period all construction and energy use in the structures throughout the United States must be 100% powered by renewable energy. (This can be done by amending building code)

In addition, the governments must impose laws, rules and regulations whereby the utility companies must comply with a fair “NET METERING” (the buying of excess generation from the consumer at market price), including the promotion of research and production of “renewable energy technology” with various long term incentives and grants. The various foundations in existence should be used to contribute to this cause.

A mandatory time table should also be established for the automobile industry to gradually produce an automobile powered by renewable energy. The American automobile industry is surely capable of accomplishing this task. As an inducement to buy hybrid automobiles (sales tax should be reduced or eliminated on American manufactured automobiles).

This is a way to expedite our energy independence and economic growth. (This will also create a substantial amount of new jobs). It will take maximum effort and a relentless pursuit of the private, commercial and industrial government sectors’ commitment to renewable energy – energy generation (wind, solar, hydro, biofuels, geothermal, energy storage (fuel cells, advance batteries), energy infrastructure (management, transmission) and energy efficiency (lighting, sensors, automation, conservation) (rainwater harvesting, water conservation) (energy and natural resources conservation) in order to achieve our energy independence.

"To succeed, you have to believe in something with such a passion that it becomes a reality."

Jay Draiman, Energy Consultant
Northridge, CA. 91325
Feb. 22, 2007

P.S. I have a very deep belief in America's capabilities. Within the next 10 years we can accomplish our energy independence, if we as a nation truly set our goals to accomplish this.
I happen to believe that we can do it. In another crisis--the one in 1942--President Franklin D. Roosevelt said this country would build 60,000 [50,000] military aircraft. By 1943, production in that program had reached 125,000 aircraft annually. They did it then. We can do it now.
"the way we produce and use energy must fundamentally change."
The American people resilience and determination to retain the way of life is unconquerable and we as a nation will succeed in this endeavor of Energy Independence.

The Oil Companies should be required to invest a substantial percentage of their profit in renewable energy R&D and implementation. Those who do not will be panelized by the public at large by boy cutting their products.

Solar energy is the source of all energy on the earth (excepting volcanic geothermal). Wind, wave and fossil fuels all get their energy from the sun. Fossil fuels are only a battery which will eventually run out. The sooner we can exploit all forms of Solar energy (cost effectively or not against dubiously cheap FFs) the better off we will all be. If the battery runs out first, the survivors will all be living like in the 18th century again.

Every new home built should come with a solar package. A 1.5 kW per bedroom is a good rule of thumb. The formula 1.5 X's 5 hrs per day X's 30 days will produce about 225 kWh per bedroom monthly. This peak production period will offset 17 to 2

4 cents per kWh with a potential of $160 per month or about $60,000 over the 30-year mortgage period for a three-bedroom home. It is economically feasible at the current energy price and the interest portion of the loan is deductible. Why not?

Title 24 has been mandated forcing developers to build energy efficient homes. Their bull-headedness put them in that position and now they see that Title 24 works with little added cost. Solar should also be mandated and if the developer designs a home that solar is impossible to do then they should pay an equivalent mitigation fee allowing others to put solar on in place of their negligence. (Installation should be paid “performance based”).

Installation of renewable energy and its performance should be paid to the installer and manufacturer based on "performance based" (that means they are held accountable for the performance of the product - that includes the automobile industry). This will gain the trust and confidence of the end-user to proceed with such a project; it will also prove to the public that it is a viable avenue of energy conservation.

Installing a renewable energy system on your home or business increases the value of the property and provides a marketing advantage.

Nations of the world should unite and join together in a cohesive effort to develop and implement MANDATORY RENEWABLE ENERGY for the sake of humankind and future generations.
The head of the U.S. government's renewable energy lab said Monday (Feb. 5) that the federal government is doing "embarrassingly few things" to foster renewable energy, leaving leadership to the states at a time of opportunity to change the nation's energy future. "I see little happening at the federal level. Much more needs to happen." What's needed, he said, is a change of our national mind set. Instead of viewing the hurdles that still face renewable sources and setting national energy goals with those hurdles in mind, we should set ambitious national renewable energy goals and set about overcoming the hurdles to meet them. We have an opportunity, an opportunity we can take advantage of or an opportunity we can squander and let go,"
solar energy - the direct conversion of sunlight with solar cells, either into electricity or hydrogen, faces cost hurdles independent of their intrinsic efficiency. Ways must be found to lower production costs and design better conversion and storage systems.
FEDERAL BUILDINGS WITH SOLAR ENERGY – Renewable Energy
All government buildings, Federal, State, County, City etc. should be mandated to be energy efficient and must use renewable energy on all new structures and structures that are been remodeled/upgraded.
"The goverment should serve as an example to its citizens"
Jay Draiman

Northridge, CA 91325
Email: renewableenergy2@msn.com
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Old 23rd-February-2007, 03:24 AM
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WHAT I DON'T NEED IS THIS KIND OF CRAP. IS THERE NO ESCAPE FROM PEOPLE'S POLITICAL AGENDAE?
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Old 23rd-February-2007, 02:27 PM
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Default Re: PV output considerations on overcast days -- some questi

Quote:
Originally Posted by Captain Pike
Today, it's bright out here in Maine, but overcast -- no bright sun shines.

What happens to a large array of PV cells on a day like this?

I am keeping a log all the days when we have bright sun here. I'm going to use this data along with my electricity usage information to try to sensibly design a PV-inverter-battery storage system.
Can I expect to draw any energy on a cloudy day, and overcast day?

Will it be necessary to build a small prototype to measure voltage outputs, relative to the "sunniness"?

If I can expect anything from my solar array on days like this, how long can one expect to be able to draw off one's battery banks?

Lots of questions, I know. I'm just starting this thing, any input from experienced folks is very appreciated.

-- Phil
What are you hoping to run using PV?

As someone already pointed out, you don't need bright sunshine to generate power using PV. and we use an annual figure (for polycrystalline PV) in the UK of around 750kWh per kWp. As peak kilowatts probably don't mean much to some readers here, a figure of 95kWh per metre squared. (Old brits, or Americans will need to do their own converstion for dodgy imperial units!)

Over here, most people live within easy reach of the national electricity grid, so we have few battery backup systems. When the sun has set (and you want power) we just pay the utility for power. When the sun is strong. they buy back what we don't need.

I'm interested in what you need to power and why you want to use PV to do it.

MM
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Old 24th-February-2007, 07:33 PM
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Default What am I doing, exactly?

I will be designing and building a new home and want to give a lot of consideration towards using solar energy. I have decided to build an interim system in my present home so I can make intelligent choices down the road.

So my needs will be typical: I want to use efficient but conventional appliances. I'm willing to make a significant investment to achieve some level of independence. I live in the Northeast United States, so there are some challenges.

I'm hoping to learn from people here who have a lot more experience than I.
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