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Sun Volt

Sun Volt Solar

earth, the final frontier

Clean Energy, Clean Environment

We are at a cross roads in human history, we can choose to continue on as we have been, or we can make a change to improve our future and quite possibly the future for several generations to come. We are here to promote energy independence, a better environment, a secure future and a higher return on investment for your hard earned dollar. It is what I believe in, it is why I am in the solar business.

Solar pool heating

17 Jun 09 | solar thermal

Summer is here and the pools are open, if not a little bit chilly.  Many folks and municipalities with swimming pools extend the swimming season by heating their pools.   Most use some sort of propane or natural gas system to heat the pool water, I have even seen a few heat pumps.  That sounds expensive.  Solar pool heating has been around for a long time and it relatively easy and inexpensive and simple to implement.

I was driving down the road this morning on my way back from an appointment and I saw this:

Enersol unglazed swimming pool heating solar collectors

Enersol unglazed swimming pool heating solar collectors

Just out of the picture to the right is the swimming pool that these collectors service.

Enersol pool heating system

Enersol pool heating system

I had to stop and take a few pictures. According to the sign, this pool is owned and maintained by the Home Owner’s Association (HOA) for the housing development just down the street.

These look like Enersol S-1000 collectors.  They are made of plastic and come in a roll.  To increase the side of the collector system, simply add more collector rolls on the end of the string.  The existing pool pump circulates pool water through them by use of a temperature controlled diverter valve.  I lifted this diagram from their site.  Looks pretty efficient and likely gathers a lot of heat on a sunny day.

The wood frame mounting rack that this installation uses looks first rate, my only comment on it is I think I would put a little more tilt to the south to gather more heat during the spring and fall seasons.  Then again, this is in the middle of the Catskill Mountains, altitude around 2,000 feet AMSL.  When it is raining almost everywhere else, it snows here.  Perhaps there is no spring or fall swimming season, only summer.

In any case, they are likely saving a good deal of money heating the pool this way.  The only other comment I have is there are no state or federal subsides for solar pool or jacuzzi heating.

Here are a few more pictures of this installation:

Enersol pool heating collectors on a wood framed rack

Enersol pool heating collectors on a wood framed rack

Solar heated pool

Solar heated pool

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17 Jun 09 | solar thermal | Comment (1)

National Security: Another reason to install a solar system

13 Jun 09 | Commentary

The great majority of the energy used in the United States (and the rest of the world) is hydrocarbon based fossil fuels.  That is no big news flash.  For the sake of argument, I am going to set aside the environmental consequences of burning massive amounts of fossil fuels to sustain our society.  There is no impact climate change, no danger from emitting Nox, Sox, Mercury, U235, Thorium, etc.  There is no environmental impact from drill wells, or removing mountain tops to get at coal deposits.

There are, however, several national security issues with the continuing the current method of generating power, transporting goods, growing food, national defense,  and so on.  These are:

  1. Transportation requires mostly liquid fuels produced from crude oil.  The US crude oil production peaked in 1971.  Since that time, we have been importing more and more oil from outside sources, which often tend to be either unstable, dangerous, or repressive dictatorships.  Not the type of source that can be relied on for vital energy supplies.  Additionally, many oil industry experts feel that we have either reached peak oil production or are about to reach peak oil production.
  2. Electrical generation in the US is mainly accomplished by burning coal.  The US has vast reserves of coal buried in the mountains of Appalachia.  The issue with coal is fly ash, a byproduct of coal fired power plants.  The Department of Homeland Security has deemed fly ash storage to be too dangerous to reveal to the public, according to Senator Barbra Boxer (D, CA).
  3. Industrialized agriculture relies heavily on nitrogen based fertilizers.  Most of these fertilizers use natural gas as a raw source of nitrogen.  Natural gas is one of the few fossil fuels that cannot be easily transported long distances via shipping, rail or truck transport.  It must use a pipe line.  That in turn means that all the natural gas we use in this country is produced in North America, the majority in the US.  Eventually, this resource will be depleted like any other.
  4. Military infrastructure depends heavily on liquid fossil fuels to power aircraft, ships, fighting vehicles and transportation.  It would be extremely expensive (tax payer dollars) to retool the entire US military to run on alternative energy, therefore, fossil fuels would be better used for national defense.  Perhaps someday we will not need a huge military, but that day is not here yet.

Conservation and careful planed use of the existing reserves of fossil fuels may extend there availability while we transition from unsustainable to sustainable energy sources.  Installing alternative energy systems such as solar, small wind, microhydro decreases the amount of fossil fuels used in small increments.  Every little bit helps.  This is known as distributed generation, which is also much harder to target and or disrupt on a large scale.

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13 Jun 09 | Commentary | Comments (0)

Hot Water tank stratification

03 Jun 09 | Solar Hot Water

There are many considerations to ensure that a solar domestic hot water system will perform at it’s optimum. The collectors should be facing south, tilted to latitude, unshaded,  etc.  One consideration that is usually not thought about or understood is the storage tank.  Like any energy storage system, there are some physics that accompany a hot water storage tank.

Stratification simply means to divide into layers.  Heated water rises because it is less dense than cold water.  The warmest water will be found in the layer right at the top of the tank, hence, most tanks have their hot water outlet at the very top of the tank.

When pumping water out of a solar storage tank, through a heat exchanger and back again, it is very important not to completely mix the water in the tank.  In most SDHW systems, the temperature sensor for the storage tank is at the very bottom of the unit.  If the tanks gets mixed, chances are the collector temperature and the tank temperature will reach equilibrium and the system will shut off.

If the solar storage tank water is pumped slowly, so that the tank stays stratified, the system will net much more heat.  This works especially well in a two tank system where tank number one is the solar tank which pre-heats the water going into tank number two, which is the back up heating system.  If done correctly, both tanks will  have a thermocline about 1/3 up from the bottom of the tank.

There are two good ways to accomplish water side heat exchanger pumping without breaking the solar tank stratification.

  1. Use a small ac pump, such as a TACO 003B and throttle the output side of the pump with a ball valve.  This pump uses very little electricity (rated for 42 watts, 115 VAC) and therefore is pretty efficient.  Restricting the flow slightly with a ball valve will not hurt it.  The water going into the heat exchanger from the solar tank should be about 5 – 10 degrees (Δt = 5-10° F) cooler than the water coming out.
  2. Use a PV powered DC pump.  There are two DC pumps that run directly from a 12 volt PV panel, the Liang D5 series and El Sid.  These can also be throttled on the output side for temperature rise of 10 degrees from input to output.    The advantage of this system is that the pump speed will adjust to the available sunlight (thus available heat) making the system more efficient.  The disadvantage is it is more expensive.

Experience shows that a good rule of thumb is 0.0125 gallons per minute per gallon of storage.  Therefore, for an 80 gallon storage tank, optimum flow rate on the storage tank side of the heat exchanger would be 80 gallons x 0.0125 = 1 GPM.  For a 120 gallon tank, 1.5 GPM and for a 240 gallon tank, 3 GPM.  This will generally give a 10 degree temperature difference between the top and bottom of a vertical tank.

Tank stratification is an important design factor that is often not thought of when a dual pumped internal or external heat exchanger system is installed.

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03 Jun 09 | Solar Hot Water | Comments (0)