12

Exergy PV is generally superior to solar thermal because it produces a higher-quality energy: electricity rather than low-grade heat: 1kWh of electricity has more exergy than 1kWh of low-grade heat. As you say, PV's efficiency tends to be significantly lower than solar thermal, in straight watt-for-watt terms, which means less power per unit roof area. ...


9

It is not, necessarily The initial capital cost of a plant is not the same thing as its lifecycle costs. The best way to analyze the cost impact of an energy source is to look at the total expected costs over the lifetime of the plant, and compare to expected energy generation. This gives you a simple measure that you can use to compare systems. There are ...


9

I will answer your question from a different approach, which is practicality rather than raw efficiency. You asked if there are advantages to heating water using solar PV instead of direct solar hot water. The first potential advantage is how the variation throughout the year can be handled. In a modern grid-tied solar PV system, you can bank electrical ...


8

I only have one anecdote and avague idea: An agrarian schooling center (Haus Düsse) in Germany clean their PV System once a year, and clean/dirty means a difference of 10% effectiveness. However, as this is basically a small farm with lifestock, different grain treatments, lots of diesel vehicles etc. you would expect far more dust there than at a lot of ...


8

This counter-intuitive advice is actually the result of research. Unfortunately journalists are rarely qualified to cover any sort of science news, and this was no exception. I'll try to explain the result in more detail, and in a way people can understand. Most people know that dark colored objects absorb light and become warm in the sun. The darker the ...


7

You measure the temperature of the water going in to the solar panel, and the temperature coming out, and the rate of flow through. The power produced is then a simple calculation of multiplying the specific heat capacity of water, by the rate of flow, by the difference between return and flow temperatures. The energy produced is the integral of power over ...


6

There's various options depending on the level of accuracy desired. To be most useful to a general audience, not just this question's asker, I'll mention a couple rough methods: The way you should track your energy choices in general is fairly simple: monitor your energy bills monthly, before and after making the change (in this case, before and after ...


6

I can think of one big advantage, in certain instances, to using PV to drive a resistance heating element: ease of transmission. I can run a cable up, down, sideways, etc. with little difficulty, provided that it is large enough for the anticipated current. To do the same thing with pipe can be tricky, especially where you have to deal with extreme ...


6

I think this is best answered as two questions. How efficient is it to use a battery as storage when excess electricity is generated by solar panels? What are the advantages and disadvantages of using an electric car's battery for this purpose? I'll take a stab at both, but there are probably others around who can answer each one better. Question 1: ...


5

Excellent question, and I agree that much of the information is too focused on the commercial aspects. The best site I've found is http://www.builditsolar.com, which has extensive information on DIY solar thermal, along with a lot of project photos and links. The site organization may not be the best, but the content is outstanding.


5

The amount of power you consume/power costs are surprisingly unrelated to the cost effective-ness of solar power. To be more accurate, they are "slightly" related. When you install a solar panel you will start generating power. Then there will be four things that can happen. excess power will go directly towards your power supplier. excess power will be ...


4

I work and attend classes at a University in Florida. Our 100kW system has been installed for more than five years without a single cleaning. I have walked the solar field several times and can confirm that no significant dust has collected. (The angle of inclination is about 27 degrees.) But, Florida rains a lot and that helps keep everything clean. I ...


4

Here are a couple of papers published between 2011 and 2016: Ranjan, K. R., and S. C. Kaushik. 2013. ‘Energy, Exergy and Thermo-Economic Analysis of Solar Distillation Systems: A Review’. Renewable and Sustainable Energy Reviews 27 (November): 709–23. doi:10.1016/j.rser.2013.07.025. Velmurugan, V., and K. Srithar. 2011. ‘Performance Analysis of Solar Stills ...


3

STES (Seasonal Thermal Energy Storage) is, in most cases, too expensive to really be practical because of the huge quantity of the storage medium needed to supply the seasonal demand. Typically, you loose a good portion of the heat through conduction or have to invest heavily in insulated containment. I find it difficult enough designing thermal stores for ...


3

Well, first of all, it is not typical for panels to completely fail like that. I am guessing that they used an "open loop" system. The typical (and generally better) system is called a "closed loop" system. You can see the basic operation below. An open loop system puts your normal water through the panels. This leads to hard water buildup and corrosion in ...


3

The more concentrated a solar collection system is, the narrower the angle over which it will accept useful energy. While the system that you describe sounds feasible, nobody who has designed systems of this sort has found it cost effective to use concentration ratios of more than about 2 to 3 to 1. Higher is possible but presumably the practical issues get ...


3

My 40 gal electric HW heater was dying (18 years old - time to go, even for a Sears Kenmore). I had EIGHT 220 watt PV panels left from an installation (at my office), and I wanted to use them to heat water (much more efficient use than sitting in my shed for a year! Right? ). 220 x 8 is only 1760 watts. I found a new "Brand X" 50 Gal Electric HW heater ...


3

Cost is a big advantage; if you already have a hot water tank with space for an immersion heater then it is a lot cheaper to add a small photovoltaic panel then a full solar thermal system. The payback time can be very short for this. No control system is needed, as the immersion heater will just cut out when the tank gets too hot – the GCH can be set to ...


2

Regarding directly feeding a tank with a series string of panels. Don't have the figures at hand but basically figured the math on this once (maybe it was 3400 btu's per kwhr?) and remember that 1500 watts of panels will put same amount of btu's in tank as a 22 sguare foot evacuated tube collector which came out to the pv panels requiring about 5 times as ...


2

This can actually be more advantageous if you have a surplus power diversion manager. During hot seasons or sunny weather conditions, solar PV panels collect more energy nevertheless any surplus to be exported to the grid. The Solar PV surplus diversion manager uses it to heat up water instead of letting it to be exported to the grid and without affecting ...


2

For heating water, you're far better off looking at solar water heaters, which take thermal energy from the sun to heat water. The power conversion formulae for converting sunshine into electricity and then electricity into heat is about 80% less efficient than just taking heat from the sun and putting it directly into the water. This is in no small part ...


2

Depends on where you live but heating with electrical heating is likely the worst thing to do. Odds are some portion of grid's power comes from thermal sources and typical efficiency from heat to electrical power are around 50%. Unless the source is near 100% thermal energy free, heating with electricity is a double whammy: It takes twice as much thermal ...


2

Take the temperature of water going into the tank. Let a hot water tap run after sundown when the solar panel is inactive and until the temperature is stable at intake. To measure this you'll have to buy one of those digital outdoor thermometers that have a sensor with a cable. Tape the sensor to the incoming water pipe. Put some insulation on top of the ...


2

Buoyancy acts vertically, so in most circumstances the answer is "no" (or at least "not with any level of efficiency that would make it worth doing"). If you don't care about efficiency (or aesthetics), and are so hard-pressed for heat that you're prepared to invest significant amounts of time/money/energy for meagre returns, then there are a few edge cases ...


2

Really good breakdown in U.S. Photovoltaic Prices and Cost Breakdowns: Q1 2015 Benchmarks for Residential, Commercial, and Utility-Scale Systems from National Renewable Energy Laboratory. If you look at the comparisons of utility, commercial and residential solar systems in the report, initial capital costs come out to 58-66% of the costs for solar. The ...


1

I have done this sort of, in reverse. I'm a tree farmer. I get seedlings and to extend the time I can plant them I have made a cold room. This is a 12x12 foot room with 4" fiberglass + 12" strawbale insulation. Inside are 10 45 gallon drums of water on sections of pallet and 4" of styrofoam chips on top. In the winter, the door is left open and the fan on....


1

Never leave home without an air mattress. I've been observing the fools that sleep on the ground for years. The older you get the more likely you will do serious damage. Yes, the "macho" who sleeps on the ground, but only goes camping a few days a year because it's too cold. Unfortunately there comes a time in the fall where an air mattress also gets cold. ...


1

The trick is to capture the heat in a fluid that circulates through the system only when the sun is heating the fluid. That way, you get the heating with very little cooling. It makes for a more complicated system, but it's worth it; otherwise, your daytime heat collector will become a night-time heat radiator. Domestic solar thermal panels are a well-...


1

I had to quit my PV water heating experiment since the wife had to take one too many cold showers and I was in fear of waking up dead one morning with a back-brush through my skull... and the solution to critters growing in your "warm" water is a small 45 watt UV sterilizer on the output of the tank. Now that did offset cost savings a wee bit, but not very ...


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