12th July 2012

Details of Solar Hot Water Panels: the Pros and Cons of Different Types

Solar hot water panels: what they are and how they work:

Solar hot water panels are also called solar collectors. They are where the sun’s heat is collected for the solar hot water system. They are usually painted with either a selective coating, or matt black. This is in order to absorb as much heat as possible. Light usually enters through glass. This reduces heat loss.

The glazed container works like a greenhouse. The glass lets in the light, and prevents most of the heat from escaping. The black collectors can heat the water to higher temperatures in the hotter environment inside the glazed chamber than they would be able to without it. Solar collectors are essential to a solar hot water system. You can’t have a solar hot water system without them.

Types of solar hot water panels:

There are three primary types of solar hot water panels: batch, flat plate, and evacuated tube.

In batch solar collectors the water tank is inside the solar collector. The tank is either painted black or with a selective coating, while the solar collector is deep, with reflective material on the back and a glass panel on the front.

Flat plate solar collectors are the most common type of solar collector. They are defined by including a heat-absorbing solid plate of material. Fluid flows across this and soaks up the heat. A glass plate in front of the heat absorbing plate and fluid acts to trap heat.

Evacuated tube
is the most mechanically complicated of the three main collector types. It is therefore more expensive. It is also the most efficient at producing hot water, which is why they are used. They are especially good for heating water to the higher temperatures needed in industrial applications.This high efficiency means that it is possible for the systems to overheat if they are not used.

Evacuated tube collectors consist of a series of glass tubes containing either one or two pipes. These pipes contain the fluid that is being heated. Inside the glass tube but outside the pipe is a vacuum. There are two types of evacuated tube solar collectors. They are direct-flow evacuated tube collectors and indirect-flow evacuated tube collectors.

Direct flow evacuated tubes contain two pipes. One pipe contains the liquid flowing into each tube, and the other pipe carries the liquid out again. The drawback of a direct flow evacuated tube is that if one of the tubes and the pipes within it break, the system stops working. It is also difficult to replace the tubes.

With indirect-flow evacuated tube collectors, there is one pipe per tube. If a collector breaks, you only lose the heat from the broken collector. The rest of the tubes keep working and you continue to get hot water, if somewhat less hot than before the tube broke.

Other collectors:

Integrated tank solar collectors are a bit of a different topic, as the collectors are the same as the evacuated tube collectors described above, but the water tank is placed directly above them and integrated with the collectors. This reduces the complexity and expense of the solar hot water system. Unfortunately, it doesn’t work well in below-freezing temperatures without special modifications.

Solar pool heaters are often made of black rubber with water inside them, without glass. This makes them cheaper, and since the water doesn’t need to be as warm as domestic hot water the fact that it can’t heat the water to high temperatures isn’t a problem.

Pros and cons of each type of collector:

Batch:
Pro: easiest collector to make
low cost of total system
easy maintenance
Con: long time taken to heat water in the morning
batch systems are not frost-resistant
heavy collectors make them harder to roof-mount

Flat Plate:
Pro: less expensive than evacuated tube
Con: loses more heat to environment than evacuated tube. This is mainly important in cold climates and in commercial applications.
More expensive than batch

Evacuated Tube:
Pro: most efficient at absorbing heat
best variety for cloudy climates
water reaches highest temperatures
best variety for industrial applications
Con: most expensive collector type
direct flow systems are hard to repair if tube is broken and one break renders system unuseable
can overheat if hot water isn’t used

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9th July 2012

Why a Solar Water Heater Might Be the Best Form of Solar Power For You

One of the most cost-effective ways of using solar power is to buy or build a solar water heater. How they work is simple: the sun heats solar collectors which then heat your water. Solar hot water systems vary greatly in cost, design, and complexity. The simplest is a batch solar water heater. This type of solar water heater can be a DIY project that is both practical to build and useful once you’ve built it. This is only one of many possible systems, the building of some of which is much more complicated and expensive.

Solar hot water heaters are growing rapidly in popularity in the USA, but also in many other places around the world. The country with the largest number of solar water heaters is China, and the numbers there are rising explosively. Solar hot water is popular in China for a very practical reason – it is much cheaper in many areas than paying for the electric utility to heat the water. Payback time there can be measured in months. Solar hot water is also very popular in Israel.

Solar hot water is not only useful in warm climates. It is also used in places such as Germany and Canada, even in winter. However, in climates like these that have freezing temperatures special systems that use ethylene glycol in the collectors are needed if the system is to be used in the winter.

Solar hot water should be used more widely, and fortunately, that is rapidly becoming the case. Solar hot water benefits over photovoltaics:

-much cheaper to buy than photovoltaic systems
–payback time is much shorter
-easier to DIY
-most types use only renewable resources
-won’t go out if there is a power outage at the electric utility

Most solar hot water heaters do not use electricity and involve no rare earth metals, although some do use large amounts of copper pipe. This is part of why they are cheaper than many other home-scale renewable energy systems. Because passive solar hot water systems involve no electricity, they are both easier and safer to build yourself than solar photovoltaics. They are also cheaper to buy. This means that the time it will take for you to make your money back is much shorter than with photovoltaic systems.

Downsides of solar hot water systems:
-a rooftop system requires a roof of sufficient strength. Water weighs 1kg/L.
-some systems do not work in freezing weather
-hot water is more available at night than in the morning
-system you build needs to be large enough for your hot water use
-produces hot water only, no electricity

Rooftop strength is important because the collectors contain either water or another liquid, and this is heavy. Most roofs in the USA were not designed with solar hot water systems in mind, and some of them aren’t strong enough. So you should check this out before going ahead and buying or building a solar hot water heater to place on the roof. Fortunately, some systems such as batch heaters can be placed on the ground and work fine, not to mention being easier to install at ground level.

Water freezes, and frozen solar water heaters a) won’t give you any hot water, and b) are in danger of being damaged. The pipes are the most vulnerable part. There are two ways to deal with this if this is an issue in your area a) have a three-season system that you drain in the winter, or b) get a system designed for below-zero temperatures. These systems are usually closed-loop systems using ethylene glycol, which means that the liquid in the collectors doesn’t mix with the water being heated. Ethylene glycol is used because it has a lower freezing point than water.

Solar hot water heaters will still function in the winter provided that they don’t freeze, but won’t give as much heat, especially in cold, cloudy weather. You might want a tankless hot water heater for backup if your winters tend to be cloudy as well as cold.

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22nd December 2011

Pros and Cons of Solar Power: Different Types of Solar Power Compared

Have you always dreamed of having a house powered by the sun? Perhaps you are seriously thinking about it, but want to know more about your options. When most people think about solar power, they think of the classic solar panels that produce electricity. These are solar photovoltaic panels. But solar photovoltaics are not the only way to use solar energy.

Solar hot water: uses the sun to heat your water instead of fossil fuels. There are several different types of solar hot water systems available. They are usually lower tech and cheaper to install than household solar photovoltaic systems, although pricing varies widely with the type of system chosen.
Pro: cheaper to buy than photovoltaic
easier to DIY than photovoltaic
Con: will only give you hot water
too heavy for some roofs
cheapest varieties don’t work in freezing temperatures

Solar swimming pool: this is actually a very inexpensive way to heat your swimming pool. It pays for itself within a few years.
Pro: short payoff time
Con: only heats your pool water

Solar thermal: technically this includes both solar hot water and solar swimming pool systems, as well as solar cookers. It also refers to heating air by the heat of the sun.
Pro: cheaper than solar photovoltaic for the amount of energy produced
Con: heat only, won’t give you electricity

Passive solar/solar architecture: designing or renovating a house so that it gains the maximum benefit from the sun’s heat, while not getting overheated during the summer.
Pro: adds very little to cost of a new house for major reductions in heating needs
Con: hard to retrofit

Solar cooker: uses the sun to cook food. It tends to cook food more slowly – can be compared to a slow cooker. Very easy to DIY compared to other solar options. They are also inexpensive to buy.
Pro: easy to DIY
cheap to buy or make
Con: needs sun to cook food
won’t do anything other than cook food
cooks food slower than most cooking methods

Solar photovoltaic: solar electricity created using the classic solar panels. A full system for your house is expensive compared to other solar power options, but it’s more versatile. It is also possible to buy very small systems intended for charging cell phones for laptops. These are very much cheaper.
Pro: extremely versatile as electricity can be used for almost anything
Con: more technically complex than other solar methods
more expensive than other solar methods for the amount of energy acquired
high-voltage electricity produced makes DIY photoelectric more hazardous than other solar power projects.

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6th December 2011

What is Hydrogen Power?

Why hydrogen will not save the planet

Hydrogen is a gas used used as a fuel. Hydrogen gas used in fuel cells is ideally obtained from water by using an electric current to break the water molecules apart into hydrogen and oxygen, and the breaking apart of water uses more energy than is gained when hydrogen is burned. This makes hydrogen more comparable to a battery than to oil. You put more energy in than you get out. The electricity used to break the water has to come from somewhere. If it comes from coal, then your hydrogen-powered car is effectively running on coal. The energy must come from renewable sources if a hydrogen powered vehicle is to be considered sustainable.

Unfortunately, one of the main commercial sources for hydrogen today is natural gas. Natural gas is a fossil fuel and therefore nonrenewable. Given that energy must be used in order to separate out the hydrogen, it might make more sense to have a natural gas powered car in the first place.

In addition to this problem, hydrogen is a gas at room temperature. In order to have relatively small fuel tank such as can fit in a vehicle, it has to be either compressed or liquefied. In order to liquefy hydrogen, it must be refrigerated down to -159.14C, although compressing it can raise the temperature at which it is liquid somewhat. As you can imagine, doing this in a car does present technical challenges. It is easier to do in something the size of a bus. That said, it can and has been done. What happens is the technical challenges involved make the vehicle expensive. There is, however, a safety issue.

Hydrogen is not only a gas, it is a flammable and explosive one. Think of the Hindenburg. Do you really want to be driving something that is powered by an explosive gas that has been tightly compressed? What happens when you get rear-ended, or have a head-on collision? The tanks have to be very, very strong, and they had better not have any flaw or weakness. While such tanks can and are being built, there is a high potential for any failure to produce nasty results.

It might be easier, safer and simpler to have plug-in electric vehicles powered by wind, solar, hydro or geothermal energy. Or for shorter trips, that wonderful invention, the bicycle.

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28th November 2011

Residential Solar Photovoltaic Systems in the USA

For decades, residential solar has been available but has been too expensive for most people with fossil fuel powered energy so easily available. Now that the world is facing climate change and fossil fuel depletion, the equation has changed. Solar photovoltaic systems have tumbled in price since the 1970s when they were so expensive, becoming a realistic option for many more people today.

The costs of a solar photovoltaic system are front-loaded. Once you have bought and installed the system, all you have to do is maintain it to have a free source of electricity. While the world around you grapples with energy prices that oscillate wildly, you’ll be laughing. Even better, that energy is renewable and far better for the environment than electricity from coal or natural gas. Natural gas may be cleaner than coal, but it’s still a fossil fuel and is therefore nonrenewable and gives off carbon dioxide when burned.

Residential photovoltaic systems are usually under warranty for 20 years and should last 25-30 years. Some last much longer. The first photovoltaic system in the USA is still operating – it was installed in 1954.

If you want a system that includes batteries, the batteries will not last as long as the photovoltaic panels or other parts of the system and must be replaced. Battery lifespan varies dramatically depending on how often the batteries are used, how deeply the batteries are discharged, and if they are ill-treated by overcharging or being subjected to unsuitable temperatures. Some types of batteries also require maintenance which consists mainly of adding distilled water at appropriate intervals.

The USA compared to other countries

Solar power is growing in popularity in the USA, as is true in many places around the globe including such disparate locations as Germany and China. With the increasing popularity has come a drastic fall in prices. Some retailers sell solar photovoltaic modules for well under $2.00 per watt. There have also been changes in the way that solar installations are funded. There are a few companies such as SolarCity in California that will install a system on your house for no money down and then charge you a lower rate for a combination of lease on the system and the electricity you use.

The fall in price and increased diversity in payment options mean that if you took a look at solar energy earlier and dismissed it because it was too expensive, it is time to take another look.

Many places in the USA are very sunny and need air conditioning in the summer, which makes solar energy an excellent option. An example would be Southern California. You get more electricity from a solar panel in a sunny place than you do from one that is in a cloudy area, or that is shaded some of the time. Given this, you have to wonder why solar electricity is more used in Germany when the USA is far better suited to it.

The answer lies in government policy. Germany got into the renewable energy game early, supporting solar power with feed-in tariffs. The USA has done far less to encourage people to buy solar systems, and what they have done they have only started recently. It is now time for the USA to play catch up, and it’s having some problems scaling up its industry ie. Solyndra.

The USA and China – solar industry interactions

There is a gap between the interests of solar installers and the interests of solar manufacturers. Solar installers like the fact that they can get cheap solar modules from China, as lower prices mean more people are installing solar systems. American solar manufacturers are having trouble dealing with the low prices of the competition. There is some currently some antidumping litigation going on between the U.S. and China. There is some basis to it, as one of the reasons the Chinese panels are so cheap is because they are not recycling things that would have to be recycled by law in the USA. The pollution has been bad enough there has actually been protests against some of the factories. To protest in China is not a minor decision.

What this means for the home owner looking for a solar system is that you should be aware that while Chinese solar photovoltaic modules are cheap, they are also less environmentally friendly than US or German manufactured panels.

Recent solar photovoltaic developments

Solar photovoltaics are still improving. Thin film solar collectors are a relatively recent development that increases the range of things solar photovoltaics can be used for as it bends without breaking. For example, it is possible to buy solar photovoltaic shingles. Thin film is also generally the cheapest solar photovoltaic material per watt, making it a very practical choice.

There are also experimental solar photovoltaic cells including multi-junction cells, and cells based on other materials than silicon. If you can get hold of these at all, they’re much more expensive than silicon-based solar cells. You could wait for these to come out and drop in price, but experimentation and commercialization take time, and the amount of time is highly unpredictable. It could be many years until they are actually available at a price you are willing to pay.

Given the current situation with lowered prices and improved technology, if you can afford to go solar, I’d say do it!

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25th November 2011

15 Things You Don’t Know About Solar Power

  1.  Albert Einstein received a 1921 noble prize for experiments on the photoelectric effect.
  2.  10,000 U.S. households are now using solar energy to power their homes.
  3. On his African journey 200 years ago, John Herschel (a british astronomer) was able to cook food using solar power.
  4. The first large scale solar power plant was opened in 1982 in California.
  5.  Solar power comes in two major varieties: solar thermal and solar photovoltaic.
  6. Solar thermal is less technologically complex than solar photovoltaic and is much easier to DIY.
  7. In 2007, more Chinese homes use solar hot water than in all other countries combined.
  8. The price of solar photovoltaic panels has dropped by at least 200% in the past 30 years.
  9. The price of solar photovoltaic panels is currently continuing to drop.
  10. The lowest solar photovoltaic prices per watt are usually for thin film.
  11. The lowest solar photovoltaic module retail price is $1.25/watt (Oct. 2011) for thin film from a German retailer.
  12. Current (Nov. 2011) low prices are partly due to a glut of polysilicon on the market from Chinese manufacturers, some of whom are going out of business.
  13. There are pollution problems at some Chinese plants producing polysilicon.
  14. Germany uses more solar photovoltaic power than the USA despite having a climate less adapted to it.
  15. Photosynthesis has been in use on Earth for 3.5 billion years.
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24th November 2011

Solar Power: What It Is, and Why We Should Care

The need for solar power

The Earth is facing a multi-headed environmental crisis. These problems may seem enormous, but we are not powerless.  There is a great deal we can do to take control over our impact on the Earth and its biosphere.  The tools to do so are not yet to be invented.  We already have them, and they’ve been available for years.  We just have to do the work to change the way we do things. One of the main dangers is climate change, which is currently being driven by fossil fuel extraction. This means we need to reduce fossil fuel use drastically.

But we will still need a power source. This is where solar power comes in, along with wind, small hydro, biomass, geothermal and other renewable energy sources. Some include nuclear, but I’m not going to get into that debate right now.

Solar power, in both its thermal and solar photovoltaic forms was discovered many years ago.  It has been used in various ways since – you’ve probably used a solar powered calculator, tried to burn something with a magnifying glass when you were a kid, and seen photographs of spacecraft with their solar panel wings. We can do far more with it than we have so far.

In its thermal form, people have been making use of solar for far longer – think solariums, greenhouses and orangeries. Then of course there’s plants and photosynthesis. Starting with cyanobacteria and other algae, they’ve been using it for at least 3.5 billion years!

Solar power’s two flavors: solar thermal and solar photovoltaic

Solar photovoltaic transforms light from the sun into electricity.  If you want to light your home with solar, you need to use solar photovoltaic.  This form of solar energy is more versatile than solar thermal since you can use electricity for almost anything, but is also more technically complicated and expensive to install for the amount of energy produced.

Solar thermal uses the sun’s energy in the form of heat. It is frequently used in the form of solar hot water systems, as well as pool heating, greenhouses for growing plants, solar cookers, solar dehydrators, and passive and active heating for the house. Solar thermal is a lot easier and more practical as a DIY project than solar photovoltaic.  The materials are often cheaper and less technically complicated.  It’s also safer if you have less skill with electrical circuits, since you aren’t working with high voltage electricity.

Why solar power is practical, and how to make it work for you

Solar photovoltaic power has undergone major improvements in recent years and has become a lot more affordable.  There are now many solar photovoltaic modules with a price of under $2.00 per watt.  This is vastly better than even a year ago.  There have also been changes in the way solar is marketed – a few power companies are offering to install solar photovoltaic systems on your house for free, and then charging a set price for electricity produced that is lower than their standard electricity rates.  This makes residential solar a possibility for many people who would not have been able to afford solar on their own.

With the exception of a very few power companies, most of the costs of solar photovoltaics are up front, one time costs.  If you go this route, you pay a large sum at the beginning but then have free electricity thereafter.  Under modern circumstances of fluctuating energy prices and a changing climate, this is an excellent investment if you have the money. If you’re off the grid using a generator, you can save a lot of money over time if you go solar.

If you have rather less money but have skill with building things or electronics and some basic equipment, there are also kits for making solar panels and solar installations.  Remember that solar thermal is usually easier and safer as a do it yourself project than solar photovoltaic.

Of course, you might be more interested in other renewable energy options. There will be more articles on these subjects on this site soon.

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10th October 2009

Green Energy Jobs: Engineering and Technical Positions

Green engineering positions typically want an undergraduate degree in engineering or closely related discipline, although a high school diploma with four years of technical and engineering experience may also be considered acceptable. There may also be guild requirements. Many of the engineering jobs are electrical, electronics, or IT positions.

Positions labeled as technician often don’t require a full degree and may be more accessible to those trying to enter the field. They often expect an Associate degree or several years of experience in the field. Engineering and technical positions aren’t open to high school graduates without experience in the field. Mechanics are a different story altogether, and often require a lot less training than engineers.

General Electric is currently hiring a lot of people for these positions. However, when working for energy companies it’s a good idea to check whether the particular projects you’ll be working on are actually green. If you’re working with coal, it is not a green job, even if you found it on a green energy jobs board.

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28th September 2009

Do DIY Solar Photovoltaic Panels Work? And Are They Worth Your Time, Effort, and Money?

There are a lot of ads for build-your-own solar panels on the internet, including on this site. I have no control over what ads do or do not appear, but felt a bit of research as to whether DIY solar panels were possible or cost effective was in order.

Solar Panel Price Comparisons

When sites say ‘build solar panels for under $100!’, they often seem to be comparing the materials cost of the homemade panel to the cost of an entire solar photovoltaic system which (for a house) usually includes multiple panels, an inverter, a charge controller and sometimes batteries. This is not comparing the same thing. A true cost comparison would be one of two things: the cost of the entire system, or the cost per watt of power produced by a single panel.

The full cost for a DIY solar photovoltaic system includes the number of panels that you wish to build as well as buying or building all the other parts of a system. Also include your time that you will be spending building the panels and mounting racks and then wiring and installing everything. A single solar panel by itself is not much use for home applications without an inverter and charge controller, and one solar panel will not power an ordinary house. Costs for solar panels are usually a little over 1/3 the price of an installed system, so while they are a major component they are not the only component.

Comparing Solar Panel Prices: Price Per Watt

The usual method of comparing the prices of solar panels is price per watt. For example, if a 60 watt panel is built for a materials cost of $104.85, as the maker of mdpub.com did, the price per watt is $1.75. The average price per watt for a commercially made module of over 125 W is $4.39 as of September 2009. Prices for smaller modules are generally higher per watt, so the home-made panel looks pretty good. So yes, it is possible to build a solar panel for less money than you would pay for commercial one. But there are several caveats:

  • This is presuming no materials were ruined while you learned how to make the panel
  • This is presuming that you manage to make the panel work properly
  • This is counting your own labor cost as $0
  • This is assuming the you do not have to buy soldering equipment or paint, plexiglass, wire, or screws in order to make the panel since the author of this site had them on hand
  • The person who made the solar panel used as an example has also built a wind turbine and a jet engine

DIY Installation of Solar Photovoltaic Systems

Once you have made your panels, will you be installing and wiring everything yourself or will you get someone else to do it? The level of skill required is an important consideration because installing solar photovoltaic systems means working with electricity, which has a certain amount of inherent danger involved. On-grid residential solar power systems usually involve high-voltage electricity, which increases the danger if you do zap yourself.

So is Building Your Own Solar Panels For You?

I would not want to try this myself, nor do I have the equipment I would need. If you have to go and buy the equipment and then teach yourself how to use everything I would not advise attempting to do it yourself. If, on the other hand, you are an electrician with a large workshop looking for a project, building your own photovoltaic system might be worth another look.

Sources:

http://www.mdpub.com/SolarPanel/index.html

Cassandra Sweet. Sept 8, 2009 Let the Sun Shine. The Wall Street Journal

Solar module retail price environment Sept. 2009

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18th September 2009

Green Energy Jobs: Administration and Management

Like all companies, green energy companies require people to organize all the work that’s being done. Someone to do the payroll, someone to hire people, someone to make sure people do the things that need to be done.

Requirements for administration and management positions in green energy are not very different from requirements for similar jobs in other industries. However, some experience with construction or renewable energy is usually preferred, and is required for some positions.

Check the requirements of the individual job you are applying for carefully. Requirements vary greatly between jobs. If it doesn’t say a certain type of experience is required, it probably isn’t. Don’t avoid applying because you assume a certain type of experience is required.

If you have any experience in construction or renewable energy, let them know. It could be the selling point that gets you the job. Experience in administration, management or customer service as related to the duties of the position should be emphasized, especially if you lack experience with green energy. Display the skills you have, and emphasize your willingness to learn those you lack.

In addition to jobs labeled as administrator, manager, or customer service specialist, there are a great many jobs in the solar industry that require managerial skills in addition to technical skills. For example, senior engineers are often required to do administrative tasks, and individuals with administration experience are preferred for these positions.

A few solar energy companies that hire for administration and management positions:

Borrego Solar

Conergy

Juwi Solar

SolarCity

or check out Green Energy Job Search Sites

Alternative Energy.com

Green energy jobs online

Renewable Energy World

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