According to the Customer Sited Tier Program released on June 29, 2010:

The following guidelines are expected to be incorporated into the solicitation(s):

1. Eligible measures are solar water heating for residential (single and multifamily), commercial buildings, and non-profits that replaces or displaces electric water heating. Equipment and systems must be certified by the Solar Rating and Certification Corporation (SRCC).
2. Expected performance will be based on the Solar Rating and Certification Corporation (SRCC) estimates or standard industry software such as RETScreen.
3. Incentives will be based on expected performance in $/kWh/yr or $/MMBtu/yr up to a maximum of 40% of installed cost after all other tax credits have been applied, with a set dollar maximum for residential and non-residential systems.
4. The program will be first-come, first-served. The residential program is likely to be implemented as a simple incentive process, as the typical residential system is small and often pre-packaged.
5. Solar Thermal hot water systems will receive incentives as an alternative to electric water heating only. MWhs saved due to electric water heating replacement/supplementation with solar water heating will be calculated and scored towards the RPS goal.
6. Installers will be required to conduct annual follow-up visits for a designated period of time.

Customer Eligibility Criteria:

• customers must pay into the RPS
• new or existing homes and buildings will be eligible
• five-year warranty for the system will be required
• residential customers must have a New York ENERGY STAR® home or have a “clip board”” or walk through energy audit conducted to determine cost-effective energy efficiency measures related to electricity use. Customers will NOT be required to implement energy efficiency measures to receive an incentive.

The largest cost savings gains can be realized by those who use electric to heat their hot water.  As I discovered first hand, about three years ago, my electric bill dropped by 1/3 when I installed a Solar Domestic Hot Water (SDHW) system.  My electric use went from over 12,000 kWh per year to just under 8,300 kWh per year.  In today’s money, that equates to $600.00 annual savings in electric costs.

The goal of NYSERDA in creating this incentive is to raise awareness of ST and increase installations to the same level as PV, which is about 20,000 installation per year in NYS.   As I have outlined in the past, the benefits of ST are:

1. Less expensive than PV.  Consumers that use electricity to heat there water can make an apples to apples comparison and find that a SDHW system will cost about 10-15% what a PV system costs for the same energy output.
2. Faster payback times.  Because of the reduced costs, paybacks range in the 5-6 year time frame with fewer rebates.
3. Less regulator concerns.  A PV system requires many, many layers of bureaucracy to complete.  A ST system permitting and installation is usually straight forward.
4. Energy output from ST is stable and does not decline with time.  PV systems age and slowly reduce the power output from individual panels.  ST systems have no such issues.
5. More tolerant to shading and siting problems.  Not that a system should be intentionally installed in a shaded location, however, they will not drastically reduce their output if subject to some minimal diffused shading such as deciduous trees in winter time.

Not that I want to beat up on PV, that too is a fine system.  Solar Thermal, however, has several distinct advantages over PV, especially for a homeowner on a budget.

Their solar thermal line is Phoenix Systems collectors, line sets and pump stations.  From an installer perspective, having a prepackaged system eliminates several hours of on site work and makes installations go very fast.  Here is the equipment list for the base system:

Phoenix Classic SDHW system -

1. 2 Infinity 323 flat plate collectors
2. Dimensions: 7.09′ x 3.77′ x 0.31′ each, Area in total 54.04 sq ft
3. Stainless steel flex pipe to connect collector to line set
4. Complete pitched roof assembly kit, includes racks
5. Station type Flow-Con-C with pump built in, type WILO-STAR S21 U15
   Controller/included in solar pump station BS3 and 2 sensors
6. 6.57 gallon expansion tank with connecting kit
7. 5 gallons 50% Propolene glycol antifreeze mix

Tanks are sold separately.  The tanks are Bradford White 75 or 120 gallon with one or two double walled internal heat exchangers.   The advantages are:

1. Modular design speed configuration and installation
2. Collectors are light weight (86 lbs vs 153 lbs)
3. fast racking system
4. Stainless Steel flexible pipe set available in 50 or 75′ lengths, no soldering required
5. Corn based glycol

I look forward to working with Earthkind solar.

Ground mounted PV array after blizzard

It helps that the panels are tilted to 40 degrees, roof mounted systems likely will not shed snow like this.  Still, on a roof mounted system, the snow will melt off, it might take a little longer.  The only system I would be careful of in this climate would be an evacuated tube collector.  Because the tubes have a vacuum, no heat is transfered to the glass envelope, which is really good for collecting heat, but not so good for melting accumulated snow off the collector.

Nine percent per year seems like quite a bit, especially since inflation has been running around two to three percent. The increases of fuel costs and energy products in general has far outpaced inflation. Projected out 25 years, the cost per kWh is $1.53! I don’t expect it to get that bad, but one never knows.

Here are some solar facts:

Based on conditions here in NY state:

• The average home owner chooses to install a 4 KW DC photovoltaic system. This generates 4500 to 5000 KWh per year.
• With rebates and incentives, the final system cost is about $10-11K.
• Over the course of the system life (25 years), the electricity generated will cost $0.09 per KWh. Currently, NY electricity averages $0.158 KWh (increasing at 9% per year).
• Without inflation, that equals a savings of $29,000.00.

Also, based on conditions in NY state:

• the average home owner chooses to install an 80 SF/80 Gallon solar hot water system. This will supply a family of four with 80% of their hot water annually.
• With rebates and incentives, that system cost is around $3,800.
• Over the course of the system life (25 years), the energy converted by this system will cost $0.03 per KWh. Currently, NY electricity averages $0.158 KWh (increases 9% per year)
• Without inflation, that equals a savings of $16,500.00.

Of course, these are long term investments. In order to realize this type of savings, a homeowner will have to stay put for 25 years. That is a rarity these days.

Solar systems retain almost all of their pre-incentive/rebate value when added to a structure as a capital improvement. Here is a list of residential home improvements and the values added to a typical house:

1. Two story addition: 94%
2. Bathroom remodel: 93%
3. Major Kitchen Remodel: 91%
4. Solar System: 90%
5. Basement finish/remodel: 89%
6. Siding: 88%
7. Roof Replacement: 85%
8. Deck: 84%
9. Hot tub: 84%
10. Family room addition: 82%
11. Sun room: 75%
12. Garage addition: 70%
13. Backup power generator: 58%

Of course, if the rebates and incentives are considered, then the installation of a solar system is cash positive from day one. What this means is the homeowner pays $11-12K but gets $32,000 of additional home value. I can’t think of a better deal than that.

Sun Tracker mashup

I received an e-mail from Andrew about a Solar Site Assessment app for 3G iPhones.  I’ll let him tell the story:

I live in Vancouver, BC, when evaluating my own home for a solar installation I discovered a gap in the solar tools market. I have a lot of trees in my backyard and was interested in doing my own shade analysis assessment. So, I looked around and found expensive tools and manual sun plots, and nothing in between. At the same time my son happened to get an iPhone. I was intrigued with the built in compass and inclinometer capabilities, and putting two and two together I come up with an iPhone based solar assessment tool.

You can check out more at their website:

www.imeasuresystems.com/

I know in New York State, NYSERDA requires a site assessment be submitted for each application.  In order for a site to qualify for the NYSERDA rebates, it has to be 80% unshaded or more.  The rebates themselves are performance based, e.g. the better the site, the more the rebate.  This app has the ability to print out a site assessment, which is key.

TACO (Thermal Appliance COmpany) is one of my perennial favorites.  I have used their circulator pumps for all of my solar hot water installations.  I like them because they are efficient units, well made, rugged, easy to service and are manufactured in Rhode Island, which, last time I checked, was a part of the United States.

What has me intrigued today is their 00-VT variable speed control product line for solar hot water applications.  They appear to have integrated a Differential Temperature Controller (DTC) into a variable speed motor drive and attached it to a circulator pump.

From the TACO website:

The (00VT) circulator continually adjusts its speed, maximizing the output of the collector, increasing the usable higher temperature water throughout the day, eliminating short cycling and increasing system performance by 20%.

Features:

• All-in-One Pump and Variable Speed Solar Control
• Available in Several Sizes, 006, 008, 009 and 0011
• User Definable Line Voltage Output,
• Supports Drain Back Applications
• Freeze Protection for Open Systems
• Holiday Function, Minimizes Collector Stagnation
• Adjustable Storage Tank Maximum Setting

Makes a lot of sense to reduce the pump speed based on the Δt of the heat exchanger. This reduces electrical use of the circulator pump, increases the heat transfer efficiency of the heat exchanger and eliminates short cycling.  From the literature, I cannot tell if the pump has an full featured differential temperature controller which would eliminate the need to install a separate one.

I called the factory to ask that question, but did not receive a good reply, so the question remain unanswered.  I believe next spring I will purchase one of these units to experiment with.

The variable speed motor controller is one of two designs, either a variable frequency drive (VFD) which will work on some permanent split capacitor motors such as the 00 circulator pumps use, or a TRIAC device.  One issue with variable speed motor drives is they can often cause RFI (radio frequency interference) if they are not properly shielded and grounded.  It would be interesting to learn which type controller this pump uses and whether or not it produces RF noise.

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.

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.

1. Current and future occupants of the house or average hot water use.
2. Water supply temperature
3. Desired hot water temperature
4. 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.

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:

1. Claw hammer
2. Small pry bar
3. Hand tools including a full set of standard sockets, wrenches and screwdrivers, needle nose pliers, diagonal cutters, etc.
4. Medium and large pipe wrenches
5. Medium and large channel lock pliers
6. Vice grips
7. 18 volt cordless drill
8. Jig saw or reciprocating saw (AKA Sawzall)
9. Hack saw
10. Tubing cutter
11. Right angle drill
12. Spade type drill bit set
13. Drill bit set
14. Digital Volt Ohm Meter (DVOM)
15. MAPP gas torch, preferably something with a built in igniter
16. Pipe cleaning supplies, flux, solder, etc
17. Ridgid propress crimping tool
18. 24 foot fiber glass extension ladder
19. Small transfer pump
20. Extension cords
21. Work lights
22. Garden hose, short and long lengths, plus Female/Female end adaptors
23. 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.