Solar Energy Facts

The following questions pertain to solar energy facts. See how many you can answer correctly. Additional information is available by clicking on underlined terms within the answers. For books on solar energy subjects click a strawberry.


Solar Energy Facts Questions

     1.    What is solar energy?

2.    What is a solar house?

3.    What is the difference between a solar collector and a solar panel?

4.    How much energy is in sunlight?

5.    How much is solar energy worth?

6.    How much does solar energy cost?

7.    Why is solar energy so expensive?

8.    Why do other countries use more solar energy than the U.S.A. ?

9.    Can I install my own solar electric system?

10.  Can I install my own solar hot water system?

11.  Can I heat my house with sunlight?

12.  How does a solar cell work?

13.  How does a solar hot water system work?

14.  How does a solar heating system work?

15.  What is radiant solar heating?

16.  Is an integrated system possible?

17.  What is a solar greenhouse retrofit?

18.  What is an energy independent house?

19.  What is a multi tank heat storage vault?

20.  What is a solar thermal roof?

21.  What is a solar thermal power?  

22. How can light powered photo luminescent exit signs save energy, save money and save lives?


 Solar Energy Facts Answers


1. SOLAR ENERGY:  It's a fact that all life depends on and comes from the sun. The production of oxygen and food would be impossible without solar energy. Farmers know the value of a large field with a plentiful supply of sunlight, and now individuals all around the world are taking this boundless source of diffuse energy more seriously as the finite supply of fossil fuels dwindle.

Today less than 0.1% of our heating, transportation and power energy comes from direct sunlight although it is now possible to meet all our energy needs with this simple, renewable resource.


2. SOLAR HOUSE: A solar house is any house that makes good use of the suns energy. It's a solar energy fact that an ordinary house becomes a solar house when it gains more energy than it looses. Do you think the addition of skylights and large picture windows facing south make an ordinary house into a solar house? If these additions add a net heating value to a house that might be so, but if they lose more heat than they gain that will not be the case.  Passive Solar greenhouse additions can transform ordinary houses into solar houses, but these additions are best suited for arid sunny areas. Active solar, hydronic systems are best suited for cold climates where sunlight is minimal and extended heat storage is critical.


3. SOLAR COLLECTORS AND SOLAR PANELS: Solar Collectors transform short wavelengths into long wavelengths and trap this energy in the form of heat which is transferred and transported into a heat storage vault. Solar panels convert selected wavelengths of light into electricity. 


4. ENERGY IN SUNLIGHT: The energy from the sun  varies from place to place and is very dependent on weather conditions. Without an atmosphere 1.4 KW/m2 per hour is available, but with an atmosphere we can only count on 1KW/m2 per hour in the absence of clouds. So, if asked how much 3 hours of sunlight on one square meter is worth what would you say?


5. $ VALUE OF SUNLIGHT $: How much is one hour of sunlight on three square meter worth? Let�s see, if we�re talking about electricity and we say that electricity is worth $0.10 per KWH than 3KWH�s are worth $0.30. The problem is that PV panels have a radiant energy conversion rate of about 20% or less so three hours of sunlight on one square meter of a solar panel is worth less than $0.06

How about heat? How much is 3 hours of sunlight on one square meter of a solar collector worth if we�re talking about heat? Well 1KWH = 3400 BTU so 3KWH = 10,200 BTU.  Since one gallon of fuel oil contains 150,000 BTU 10,200 BTU�s are the equivalent of .07 gallons of fuel oil.

Now if fuel oil is selling for $2.00/gallon which it soon will be the value 10,200 BTU�s is about $0.14. You might think this is an unfair assumption since we're not taking into account the heat conversion efficiency factor like we did with the solar panel. I�m glad to see you�re paying attention and you are right about this. The heat transfer efficiency of a solar hot water system is between 50% and 70% the same as oil burner heat transfer efficiency. Since the heat transfer efficiency for an oil burner is about the same as solar collector and the price of oil is $2.00/gallon than the value of 3 hours of sunlight on one square meter is worth actually $0.14.

How about the value of heat energy over the period of one year on a roof (20� x 50�) tilted south at a steep pitch designed to maximize heat gain?

The surface area of the roof is 1000 sq ft or 95m2.
The solar energy available (for north central USA ) over the period one year on one square meter is 1500KWH. So on 95m2 we�d have:95x1500 or 142,500KWH or 484,500,000 BTU or the fuel oil equivalent of 3,230 gallons of #2 fuel oil. At $2.00/gallon our solar roof could save us as much as $6,460/yr. If half this energy is used for heating and half is used for electric power we could meet the residential requirements for energy independence. The question that you should now be asking is:
How much would a house like this cost?  

6. $ COST OF SOLAR ENERGY $: Let�s take a close look at the cost requirements for a typical energy independent house in a northeastern area of the United States where the total energy bill is $3,500/yr. Let�s use $2,000 for heating and hot water and $1500 for electricity.

ELECTRICITY: We�ll need to produce 15,000KWH�s to meet our yearly household electrical requirements.  That�s about 40KWH per day. Since an average of 4KWH/day is available we�ll need a 10KW system to meet our yearly electrical requirements.  The electricity produced by this 10KW system would have a value of about $4.00/day and require about twenty five 2 m2  panels that would occupy a surface area in excess of 600 square feet. An installed system like this could easily cost $100,000 at $10/watt. Incentive rebates could cut this cost in half, but even at a cost of $5/watt the payback period would be about 30years. If your good friends with an electrical contractor or if you do your own work you might be able to do a little better, but this is still a major investment for a product that has a live expectancy of 20 years. If the price per watt comes down to $1/watt or the price of electricity increases to $1/KWH I�m sure the ugly power lines that cut across our towns would soon be replaced by roofs decorated with PV panels. Until that time I�ll be exploring the possibilities of solar thermal energy.

HEAT: For our well insulated house in the north east we�ll need 1000 gallons of oil per year. Some people will need more, but remember our budget is only $2,000/year for heat and hot water and we�re paying $2.00/gallon. OK the first thing we need to do is convert 1000 gallons of fuel oil into an energy equivalent expressed in terms of KWH�s. You should do this with me to make sure my calculations are correct. I like to round my numbers off to keep things simple. I hope you don�t find this confusing.

1000 x 150,000                        = 150,000,000 BTU
150,000,000 BTU/3400          =           44,200 KWH  
442,000 KWH is our heat energy requirement for a year.
Since 1 m2 collector will harvest 1500 KWH/year.

44,200 KWH will require a surface area of 29.5 m2 to harvest this much energy. Since winter sunlight is more difficult to come by than summer sunlight lets change this estimate to 40 m2. Since most commercial collectors are 2 square meters you�d need 20 of them spread out over an area of 450 square feet to collect this much heat. This many commercial collectors installed with a sufficient number of commercial solar hot water tanks and a radiant heating system would cost about $100,000. If you built and installed your own solar heating system it would cost you about $10,000  

SUMMARY: To summarize. I am saying that it will typically cost a person between $100,000 and $200,000 to convert their house into an energy independent house using commercially available solar application retrofit products and commercial installers. Even at a cost of $200,000 this kind of retrofit may not be feasible if the roof is too small or oriented in the wrong direction. Sounds like a lot of money huh? It is a lot of money. This is why most people don�t take solar energy seriously. You could dabble with a few solar toys if you like, but if you are seriously interested in declaring energy independence at a reasonable price you should consider designing and building an energy independent house from the ground up for not much more than a conventional house. The more involved you get with the process the more you will save.

7. Why is solar energy so expensive?

There are many reasons why solar energy is so expensive. I�ll try to shed light on a few of them.

       a.    Competition is minimal.
       b.    Government regulations will not allow house owners to install their own systems.
    c.    Architects are reluctant to approve innovative unproven solar house designs.
    d.    Builders find that it is not profitable for them to spend excessive architectural                 fees on designs that are not mainstream and salable.

e.    Our government, who should be demonstrating a leadership position in the promotion and use of solar energy, is the primary offender of energy conservation and has no interest in the promotion of a sustainable culture that might threaten the aristocracy.

f.      The price of oil is maintained at an artificially low price by government subsidies and special interest groups.

g.    Most people are too busy dealing with the problems of day to day survival to be concerned with the headache of a long range investment like solar energy.

h.    Fossil fuel oil corporations, who control our economy are doing all they can to discourage the proliferation of alternative energies.

i.       We have become addicted to fossil fuel energy concentrates the way a child becomes addicted to candy.  


 8. Why do other countries use more solar energy than the U.S.A. ?  
Oil is three or four times more expensive in many non American countries. Solar energy alternatives are less expensive than fossil fuels and grid power. It�s as simple as that. If you had to pay $7 gallon would you consider the possibilities of solar?  

9. May I install my own solar electric system?  
Legally speaking, most state regulations prohibit individuals from installing their own system even though these installation fees are excessive. If you do install your own system you could easily cut your bill in half, but than you wouldn�t be entitled to a rebate.

 10. May I install my own solar hot water system?  
Legally speaking, most state regulations prohibit individuals from installing their own solar hot water system, but the rebates are at best minimal and very difficult to apply for. The penalty for installing your own system could be as harsh as an order to remove it when you sell your house.  If you think you have the necessary plumbing skills go for it, but don�t expect your insurance company to cover any plumbing damages.  

11. Can I heat my house with sunlight?  
Most definitely. If you live in the south west all you need is a simple passive solar greenhouse. Northern climates require lots of insulation as well as an entire solar thermal roof dedicated to the process of gathering heat and an enormous heat storage vault for storing it. The labor and materials required to heat a house with sunlight are minimal compared with the government regulations and the building permit headaches.  

12. How does a solar cell work?  
I can show you how it works and even show you how it�s made, but the equipment needed to produce a practical solar cell is very, expensive so unless you�re a millionaire with a bottomless pit of money or a talented, dedicated machinist I�d shoot for a different profession.  

13. How does a solar hot water system work?  
Most hot water systems are designed to preheat water before it enters a conventional hot water heating system. The five parts of the system include a collector, a pump, a heat storage tank and a differential thermostat.


14. How does a solar heating system work?  
Hydronic solar heating systems
work the same way as solar hot water systems except that the stored hot water is used for house heating rather than domestic hot water systems. Hydronic solar heating systems are typically ten or more times larger than domestic hot water systems. In mild, sunny areas the hot air from solar greenhouses are often used for house heating, but hydronic systems are more suited for cold climates.  

15. Is an integrated system possible?  
Solar heating and solar hot water systems may share the heat from the same heat storage vault.  

16. What is radiant solar heating? 
Radiant heating
is a method of heating slab of material. Since the temperature of stored solar hot water is low radiant heating is preferred. This is true because the large surface area of a radiant heating system is required to obtain the same results of a conventional concentrated heat source. A warm floor is a warm house. Radiant solar heating systems circulate hot water through a network of plastic tubes into the flooring of a concrete slab. Plastic tubes are used because they will not corrode in the presence of concrete.  

17. What is a solar greenhouse retrofit?  
A retrofit is sort of an after thought. After a house is built the owner decides to add something. If a house is oriented properly and landscaping permits a fair amount of sunlight into the proposed solar greenhouse a practical method of heat gain is possible. Solar greenhouses are different than standard greenhouses in that they have a net heat gain effect on the house.  

18. What is an energy independent house?  
An energy independent house is exactly what you think it is. It�s a house without power lines hanging over the back yard. It�s a house without an oil tank attached to the side of the house, buried in the ground or occupying valuable basement space. A well planned solar house can supply all the electrical household needs and 80% of the heating requirements. Additional heating requirements can be supplemented with a well insulated, wood stove designed to burn (wood, cardboard, cereal boxes, milk cartons, and other household waste products) at a high temperature. High temperature burning results in complete oxidation without polluting the atmosphere. A well insulated wood stove releases most of its heat through the chimney. This is where heat should be collected and added to the multi tank heat storage vault.  

19. What is a multi tank heat storage vault?  
A multi drum heat storage vault system is a practical, efficient, method of collecting, storing and distributing large quantities of heat at low cost.  

20. What is a solar thermal roof?
A solar thermal roof is basically a roof converted into one giant collector. A solar thermal roof 50�x20� or 1000 sq ft could easily harvest the fuel oil equivalent contained in 3,000 gallons of fuel oil/year. The materials needed to make a solar thermal roof of this size cost about $4,000. It takes two men two days to assemble. A 3,000 gallon heat storage vault takes a full day to build. The plumbing and radiant heating system could take another day. The material cost of the entire system would be about $6,000. The problem is that most roofs are not oriented south with the steep pitch needed to maximize winter heat gain so a radical roof and house reconstruction might be necessary to make a solar thermal roof practical. This is why more thought should go into new construction and house builders should be educated about the possibilities of a solar thermal house.


21. What is a solar thermal power?
Commercial solar power plants use superheated steam to generate electricity. A residential solar hot water storage vault stores hot water system operates at a much lower temperature.
Is it possible to use this low temperature to generate electricity?
As long as a there's a temperature difference electricity may be generated. Sterling engines can operate at temperature differences of less than 150 F although the power they generate is not very significant. To increase the efficiency of power generation and use the waste heat to generate hot water for house heating we need a low temperature turbine generator but that could take a lot of government research dollars to develop. Another possibility is that we could pool our efforts and come up with with a viable low temperature solar thermal engine. Interested?

22. Photoluminescent ecoglo strips and signs store light energy and glow in the dark without any external power source. This technology is designed to save energy, time and money.


Strawberry Fields Solar Book Store
How to Build a Solar Hot Water System

Solar Collector Plans 
Energy Independent Housing 
Alternative Housing for the 21st Century 
 Active Solar    Passive Solar  
 Greenhouse Effect and the Solar Greenhouse  
Solar Energy the Alternative Energy of Choice

Heat Storage Vaults
Gallery of Solar
Houses Houses  
Photovoltaic Electricity Animation
  Solar Water Heating Animation  
Our Sun and Our Future

Five Solar Thermal Principles

Solar Heating

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