Sun Volt Solar Blog

Solar Electricity Handbook

I was contacted by Mike Boxwell, author of The Solar Electricity handbook (ISBN 978-1-907215-01-8, Green Code Publishing, Warwickshire, UK. 2009) and asked if I would do a blog post about it.

I went to The Solar Electricity Handbook website and browsed through the first few chapters. It seems the book is thoughtful and well laid out. As Mike said in his e-mail:

The book deals with the practicalities of using solar power to generate electricity successfully and in the most ecologically friendly ways and is aimed at the DIY installer and enthusiast.

It is not a work that I would especially refer to for my every day solar installation business. However, for a do it yourselfer that has some good working electrical knowledge and skills, it might be just the thing needed to answer some of the more obscure solar questions.

The web site also has some good links, calculators and other information. So, if you have stumbled onto this blog looking for do it yourself information, check out The Solar Electricity Handbook.

Tags: diy, Solar Electric

01 Jul 09 | Solar Electric | Comments (0)

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

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

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

Solar heated pool

Tags: solar pool heating, solar thermal

17 Jun 09 | solar thermal | Comments (0)

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:

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.
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).
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.
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.

Tags: agriculture, clean coal, national security, peak oil

13 Jun 09 | Commentary | Comment (1)

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.

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.
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.

Tags: physics, SDHW, solar thermal

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

Delinquent Clients

20 May 09 | General Business

This happens to every business. You provide a service and the customer decides not to pay. There are several reasons for this, some of which are predictable and thus can be avoided. They include:

Sudden loss of income. During the installation the customer looses his or her job. This happens and there is almost nothing that can be done about it. My business model has always relied on down payments, e.g. 1/3 on order, 1/3 on delivery and 1/3 on completion of a job. Therefore, at any point in a project I am not that far behind.
Inability to pay. This is completely preventable and can be determined during the early stages of a project. It is the reason why a contractor should always completely explain the costs and get a signed contract with the customer. If there are any doubts, as for a different payment plan, e.g. 1/2 on order, 1/4 on delivery and 1/4 with completion of the project.
The customer is an asshole. This one should be apparent during the sales presentation. Things to look out for; customer has a past history if stiffing contractors, suing contractors, seems dishonest, etc. Sometimes it is nothing more than a bad feeling. Often times when this happens my schedule suddenly becomes booked solid for the next 6 - 12 months.

It is important to follow up on things. This means sending out an invoice promptly when payment is expected. After 30 days, a statement of monies due and a follow up phone call. Often times, simply asking if they received the invoice and statement, then asking when you could expect a check will suffice. Sometimes not, however.

In many cases, things can be worked out. In case number one, often times a payment plan can be put into place. Generally, these people want to do the right thing, but due to circumstance beyond anyone’s control, they cannot.

In the case where the customer never had the ability to pay, this is the fault of both parties. The customer is at fault for lying and the contractor is at fault for not checking out his potential customer before starting work. Chances are that this customer will never have the wherewithal to pay, nor would any legal proceedings be fruitful. This may end up being a business loss that is written off at the end of the year. It does happen occasionally, but a credit check can almost eliminate these situations.

If you are dealing with a customer that can clearly pay but for some reason has decided not to, then there is something called a Mechanic’s Lien. This is a last resort measure and requires a solid paperwork trail. The requirements vary from state to state, however, in New York, a Mechanic’s Lien must be filed within four months of the completion of work. What then happens is the property cannot be sold, transferred or refinanced without the lien being satisfied. Often times, on a new construction, the bank will not release the next draw until the lien is satisfied. It becomes public record. I would not go to this well very often, but if you are out a lot of money, it is a way to get payment.

In short, if you want to stay in business, then you need to get paid.

No related posts.

Tags: Add new tag, Business administration

20 May 09 | General Business | Comments (2)

Can plastic piping be used in a solar hot water system?

12 May 09 | Solar Hot Water, Training, solar thermal

Short answer: Don’t do it.

Plastic piping such as PEX, PEX AL PEX, PVC, ABS, etc. can be safely used with hot water systems, radiant floor heating and so forth. It is much cheaper and usually easier to work with than copper or stainless steel. That being said, it is not appropriate for use in any solar thermal application.

Solar thermal systems have much less control over high temperatures than conventional fossil fuel based systems. Summer time collector stagnation temperatures can easily reach 300° F. At these temperatures any plastic piping will melt. This will cause the Heat Transfer Fluid (HTF) to leak creating a big mess and likely an insurance claim. The only type if piping that should be used in a collector loop is copper or stainless steel.

Even copper fittings with rubber gaskets (AKA Pro-Press or Viega fittings) are only rated for 250° F. They should not be used in a solar loop either.

It is worth the extra time, effort and expense to solder copper piping and or purchase stainless steel tubing for use in the solar loop. This will ensure that the system works well for years to come with no leaks and no call backs.

Tags: installation tip, piping, SDHW

12 May 09 | Solar Hot Water, Training, solar thermal | Comment (1)

Is it a good time to buy a solar system?

07 May 09 | Commentary

Short answer: It is always a good time to buy a solar system.

Now is especially good however because there is an overstock of Photovoltaic panels and Thermal collectors. Prices are lower than they have been in several years.

Of course, going against this over supply is a general lack of credit and/or cautious outlook. That is understandable in any circumstance because solar systems require a large outlay of money, more so for PV.

Here is a short list of reason why now would be a good time to install a solar system:

Lower prices. Most distributors have an overstock of PV panels on their hands that they would love to move. Prices have dropped about as far as they can go without some companies going out of business, which would be bad.
Installers (like my self) are looking to fill in some installation dates on our calendars this summer.
Energy prices are relatively low but that will change once the economy begins to recover even a little bit.
Excess government borrowing and huge national debt is likely to trigger high inflation. Now would be a good time to get your energy prices locked in for the next 20-30 years.

Increased oil prices may be coming sooner than most people think. Right now Crude prices are slowly moving up to $60.00 per barrel. Motor fuel is inching up slightly faster because refiners have closed down several refineries to put some downward pressure on the supply side.

High inflation is almost inevitable at this point. There does not seem to be any other logical conclusion about the US financial system other than the creation of vast amounts of dollars by the Fed to bailout banks will have consequences. Look for inflation in the mid teens starting in mid 2010-11 or so.

When a homeowner purchases a renewable energy system, they in essense, lock there energy prices at a certain rate for the life of the equipment. For example, if a 2 KW PV system costs $7,000 (after incentives) installed and generates 79,000 kWh over the next 25 years, the cost of that electricity is $0.08 per kWh. Less than half the current NY state average of $0.165 per kWh. That is a great hedge against energy price inflation.

Nice try big guy

Tags: economy, Sales

07 May 09 | Commentary | Comments (0)

Calculating energy needed to heat water

05 May 09 | Solar Hot Water, solar thermal

In order to properly size a Solar Domestic Hot Water (SDHW) system, a few pieces of information are needed:

Current and future occupants of the house or average hot water use.
Water supply temperature
Desired hot water temperature
Stand by loss of heating unit

We know that in this area (Mid Hudson Valley) ground water temperature averages 53 degrees. I know this because I have personally measured the well water temperature at all of our SDHW installations. This is a good starting point.

Most people desire their hot water temperature to be between 110 to 120 degrees. There are some applications where hotter water (laundry, dish washers, etc) is desired. For general purposes 115 degrees is a good ending point.

We also can base average hot water useage on the number of occupants of any house. The rule of thumb is 20 gallons per person for the first two people, 15 gallons per person for any additional people. This means that the average family of four uses 70 gallons of hot water per day (20+20+15+15 = 70).

Standby losses for water heaters generally range from 5-10% for electric and oil fired systems and 40% for natural gas or propane water tanks.

For the purposes of Solar Hot Water, an appropriate unit of energy would be the BTU. If we were using SI units (metric) it would be the Mega Joule (MJ). Since most HVAC contractors understand things in terms of BTUs, it is easiest to use this unit.

A BTU is defined as amount of heat required to raise the temperature of one pound of liquid water by one degree Fahrenheit. That is close enough for our purposes.

Therefore, the formula to calculate energy use is:

BTUneeded= 8.34 x Gallons x (desired°F-supply°F) x Standby

Where:

BTUneeded = BTUs needed to heat the water for one day
8.34 = Weight in pounds of one gallon of water
Gallons = Gallons of hot water used in one day
desired°F= Desired temperature of the hot water
supply°F= Cold water supply temperature
Standby= Standby loss of the heating appliance

A typical family of four heating their hot water with electric or oil would expect to use:

BTUneeded = 8.34 x 80 x (115°F-53°F) x 1.10 = 45,503 BTU/day

A typical family of four heating their hot water with gas or propane would expect to use

BTUneeded = 8.34 x 80 x (115°F-53°F) x 1.40 = 57,913 BTU/day

To get an idea of cost, BTUs need to be converted to energy units that are used for electricity, oil, and gas.

Electricity has 3412 BTU per kWh. Therefore 45,503 ÷ 3412 = 13.3 kWh. Going rate per kWh is about $0.16. 13.3 kWh x $0.16 = $2.13 per day or $778.83 per year
Heating oil has 138,700 BTU per gallon. Therefore 45,403 ÷ 138,700 = 0.33 gallons. Going rate per gallon $2.459. 0.33 gallons x $2.459 = $0.81 per day or $269.19 per year.
Propane has 93,000 BTU per gallon. Therefore 57,913 ÷ 93,000 = 0.62 gallons. Going rate per gallon $2.428. 0.62 gallons x $2.428 = $1.51 per day or $549.46 per year.
Natural gas has 102,000 BTU per CCF. Therefore 57,913 ÷ 102,000 = 0.56 CCF. Going rate per CCF is $1.633. 0.56 CCF x $1.633 = $0.93 per day or $338.42 per year.

Tags: energy costs, SDHW, Solar Hot Water

05 May 09 | Solar Hot Water, solar thermal | Comments (0)

Tools for the solar installer, Thermal and hot water systems

29 Apr 09 | Solar Hot Water

Solar thermal installers deal with a different set of tools than Photovoltaic. Most solar thermal systems rely on some type of plumbing and pump system to move heat transfer fluid through a set of panels and back to a storage tank. Solar thermal panels are generally larger and heavier than photovoltaics. Drainback systems need to have all of the pipe slope back to the drainback reservoir. All of these considerations require different expertise and working requirements.

Most solar thermal installations are placed on a south facing roof. Often, a bit of carpentry is required to attach the solar collectors to the roof. This is a basic list of power and hand tools for solar thermal installations:

Claw hammer
Small pry bar
Hand tools including a full set of standard sockets, wrenches and screwdrivers, needle nose pliers, diagonal cutters, etc.
Medium and large pipe wrenches
Medium and large channel lock pliers
Vice grips
18 volt cordless drill
Jig saw or reciprocating saw (AKA Sawzall)
Hack saw
Tubing cutter
Right angle drill
Spade type drill bit set
Drill bit set
Digital Volt Ohm Meter (DVOM)
MAPP gas torch, preferably something with a built in igniter
Pipe cleaning supplies, flux, solder, etc
Ridgid propress crimping tool
24 foot fiber glass extension ladder
Small transfer pump
Extension cords
Work lights
Garden hose, short and long lengths, plus Female/Female end adaptors
Personal safety equipment such as safety climbing harness, safety glasses, heavy work gloves, etc.

In addition to the above tools, having all of the fittings and valves available on the truck saves a lot of time. I always buy extra fittings because I know that I will eventually use them. Having a spare pump and controller is also recommended. These are the only active parts in a solar thermal installation and are thus the most likely to fail out of the box.

Tags: tools

29 Apr 09 | Solar Hot Water | Comments (0)

More Solar jobs in the Hudson Valley

14 Apr 09 | Solar Electric

In the good news department, another PV company has chosen the Hudson Valley to set up manufacturing facility.

SpectraWatt, Inc., a manufacturer and supplier of advanced silicon photovoltaic cells, announced it would move its headquarters from Oregon to the Hudson Valley Research Park in East Fishkill, initially creating over 100 jobs within the first year of operation. That will go up to 150 by the time phase one is up and running in two years.The company expects to be in production early in 2010. Its first factory line will have an initial manufacturing capacity of 60 megawatts; additional lines are being planned with site capacity exceeding 120 mw within the first two years of operation.

This is a good use of excess manufacturing space at the IBM East Fishkill’s Hudson Valley Research Park. Building 334 is currently a 300 mm and 200 mm chip fab for NXP (Formerly Philips Semiconductor). The press release goes on to cite an abundance of skilled labor plus many economic incentives offered by Dutchess County and the State of New York.

All of this is good news of course, for the local community and for the solar industry. I would like to see some type of solar thermal panel manufacturer in this area. Solar heating is still 4-5 times more efficient that photovoltaics. As proven by my own solar thermal installation plus many many more in the area, it works well in this climate and can make a significant reduction in residential energy use.

Tags: manufacturing, photovoltaics

14 Apr 09 | Solar Electric | Comments (0)

Sun Volt Solar Blog

earth, the final frontier

Clean Energy, Clean Environment

Solar Electricity Handbook

Solar pool heating

National Security: Another reason to install a solar system

Hot Water tank stratification

Delinquent Clients

Can plastic piping be used in a solar hot water system?

Is it a good time to buy a solar system?

Calculating energy needed to heat water

Tools for the solar installer, Thermal and hot water systems

More Solar jobs in the Hudson Valley

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