Harnessing Solar Energy with Alternative Energy Technologies

Sep 8th 2010 at 4:21 PM



With the use of photovoltaic solar cells or PV, sunlight can be converted to electricity. Unfortunately, only about 7% to 15% of the energy hitting a PV cell can be converted to watts or energy. This is the cell’s efficiency. This means that, at best, a PV cell can produce approximately 70 to 150 watts per square meter. The current average cost per watt using PV is as low as $6 per watt, but this does not include control and support systems, which when included will increase the cost per watt between $9 to $12 per watt. can vary depending on where it is installed geographically, but rule of thumb is between 4 and 8 hours. If you assume the average of 6 hours, a PV array must produce 4Kw per hour to handle each 1kw load over a 24-hour period (4Kw x 6 hours = 24Kw). Assuming an 110w per square meter average, this means that the PV solar array footprint would need to be 218 square meters or 2,181 square feet. This is almost twice the size of a standard American roof (1,200 square feet) and would cost $28,000 ($7 per watt x 4,000 watts on the array).

Solar thermal energy (STE) is a technology for harnessing solar energy to create thermal energy. This energy can be used for space-heating, heating water and through the use of absorption chillers, cooling – air conditioning buildings and homes.

These three categories of energy consumption make up 74% of the total energy consumption in the U.S. Unlike PV, Thermal Solar collectors are very efficient. Solar thermal systems, on average, are 92% efficienct, compared to the 12% seen in PV arrays. After taking into account system loss, Thermal Solar arrays produce 750 to 950 watts per square meter, ten times more per square meter than PV arrays.

Historical costs of solar thermal systems from the power industry, including all three power sectors – heating, cooling, and water heating – on average cost one-tenth the price of a photovoltaic system. When looking at cost per watt, remember that PV is $7 to $12 per watt. The cost of a nuclear power plant is $3.50 per watt.

A thermal solar system designed by Arctic Solar on average is as follows:

• For heating water, which makes up 17% of all energy consumed in the U.S., costs $0.30 per watt; 


• For space heating, which makes up 46% of all energy consumed in the U.S., costs are $1.25 per watt; and

• For solar cooling or air conditioning, which makes up 6% of all energy consumed in the US, costs are $2.75 per watt.

non-replenishable resources. What we should focus on is the real and practical ways of achieving alternative energy goals by following a technology that can deliver today, not maybe in year 2015. PV has a place in alternative energy planning and the research should be continued, but not at the expense of today’s energy needs or our climate for the next six years.



At these costs, real power savings can be achieved. These systems are easy to install and have a 25 year life span. So in looking at our 24Kwh home used in the example above for PV, in a 6 hour solar day, a solar thermal system (800 watts per square meter) would need to be 5 square meters in size (800watts x 5 = 4000 watts per hour), (4000w x 6 hours = 24kwh). Compared with the 218 square meters of PV, there simply is no comparison. 5 square meters is 50 square feet and would easily fit on any standard 1,200 square foot U.S. roof.

Given that the Solar Thermal array produces more than 10 times the power, it can be many times smaller to produce the same power output of a PV array. We must begin thinking power, not electricity. Do we care how the water is heated? Or how the air that comes out of our vents is cooled or heated? No, we should only care in terms of costs and how it affects the environment.

Solar thermal has many more advantages. Not only is it taking the most abundant type of energy that we have from the sun (thermal), but it is also, when installed on a building or home, acts as a solar/thermal blanket, or sponge, that absorbs the thermal heat that would otherwise hit the roof of a the structure. This shading effect reduces the load of a structure and, therefore, reduces the cooling requirements for that structure. Estimates are that between 10% to 15% of the air conditioning load is reduced when a thermal solar collector is intalled on the roof of building because of the absorption of heat by the array that would otherwise be applied to the structure during daytime hours.

These systems have been, for the most part, forgotten by the main stream alternative energy sector whose sole focus is the production of electricity. The focus on semiconductor or PV and bio-technologies has given little time and development for thermal systems. It has created a welfare sector that can only survive with government grants or corporate donations – mainly because their products are not commercially viable. Arctic Solar believes that true gains in energy independence can only be realized by the use of thermal solar systems.

PV is too expensive and requires too much space or footprint to be practical in today’s economy. We continue to try and drive a square peg in a round hole by our focus on electricity and oil to handle our energy needs. Remember, it is not important how the hot air for heating arrives, or the cold air for cooling arrives, or how hot water is obtained for our homes and businesses; it is the cost and effect on our planet which is important.

The real importance is that we reduce energy requirements that come from fossil fuels and

Out of 100% of the thermal solar systems installed over the past three years, which constitutes hundreds of thousands of systems worldwide, only 0.004% were installed in the U.S. — less than one half of one percent. The rest of the world is leaping ahead and harnessing the sun in cost efficient ways while we focus on a technology whose goal is still to be cost inefficient in 2015. As in light-rail systems or mass transit, the U.S. is missing the goal as the world builds bigger and better transportation systems. Take a look at what is happening around the world in thermal solar.

Efficiency goals for the PV industry have been projected to reach 42% by 2015. To obtain this goal, an increase in technology, such as tracking systems, will drive up the complexity and cost of the support systems, which in turn will keep cost per watt high. Mass production and new approaches coupled with new technologies are the best hope to make PV a real viable solution.

Another problem with PV is the footprint of the solar array. For every 1KWh (1,000 watts used in one hour) consumed in a home or business over a 24 hour day, the system needs to produce and store 24Kw of power (1Kw x 24 hours). Solar, of course, is only power producing during daylight hours, so you must produce enough power during the daytime production hours for use in the daytime, plus an additional amount to store for nighttime use. Production time of the array

Since businesses generally consume even more power, this example gets even more impractical. If you look at the idea of very large PV arrays in the desserts of the Southwest or California, again remember that no matter if you take today’s 12% to 18% efficient solar collectors and you ignore the price per watt for construction, you will lose 10% of the electricity that is produced in transmission.

Net…Net…Net, the consumer will see at best 4% to 8% of the power generated. Simply put, photovoltaic panel arrays do not produce enough energy to be economically viable and the footprint is too large for onsite production that works. Average return on investment with a PV solar installation on a home or business exceeds 30 years, with no real reduction in power production. Building large solar PV power plants is extremely expensive and, again remember, that 10% power loss of the grid for distribution to customers.

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Sep 5th 2012 at 11:41 AM by InOutYourBox
So, do you see a solution?

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