February 08, 2010
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Solar Domestic Hot Water

Technology Name:
Solar Domestic Hot Water (SDHW)

Date Introduced in the market:
1890s

Maturity of the technology:
Established industry with continuous growth over 5+ years.

Type of energy that can be produced (i.e. thermal, electrical):
Thermal: hot water

Typical applications:
To supply hot water for domestic/household uses - such as laundry, bathing, dishes. To provide hot water for outbuilding or barn uses (see commercial hot water applications)
To reduce the use and dependency on gas and electricity for household hot water heating.

Expected Pay-Back:
With a good southern exposure and adequate space for a solar storage tank, a solar water heater will pay for itself in energy savings in 5 to 15 years under average energy costs, with a return on investment of 8-14%. It will provide 75 to 100% of summer hot water needs and 10 to 20% of your residential hot water demand in winter (40-60% over all) These cost estimates do not include the cost of the backup heat supply system. In many cases, existing water heating systems can be converted from primary to solar back-up but sometimes a different back up heating system is advised.

Range of possible dimensions and sizing considerations for the system:
The main components of a SDHW system are the collectors and the storage tanks. These components are sized depending on the hot water use of the household/ users, climate and solar exposure. Usually systems are designed to meet 75-100% of the household's hot water needs in the summer months. In colder climates, sizing a system to meet 100% of year round hot water needs will usually have excess energy to meet summer hot water needs, be very expensive and require more space than most homes have available for collectors and storage. Hot water storage tanks typically lose .15 - 1 degree/hour. For example, over 2 cloudy days, with not enough solar exposure to provide solar heated water, the temperature in a standard storage tank would drop up to 48 degrees. While insulation is important to minimize energy losses, even a well insulated and oversized storage tank will not usually maintain required hot water temperatures through successive colder cloudy days. Therefore, systems in Canada are generally designed with a back up source of heat. Retscreen is a free software from NRCan that can assist with sizing a renewable energy system. www.retscreen.net.

Other considerations in designing a SDHW system include the cold water intake temperature, desired hot water temperature, pattern of hot water use.

Collectors:
Collector sizes vary, however a common panel size is 4 x 8 feet with single family systems often designed with 1-2 panels for typical range of collector array size of approx. 3-6m². Collector array size should be determined based on the size of the storage tank chosen to meet hot water needs as well as the solar exposure and climate.
-A rule of thumb to size collectors: 1 square foot of collector plate per 1 gallon of hot water storage.

Storage Tanks:
Solar storage tanks can double as the household hot water storage tank (with 2 heat exchangers, one for the solar system and one for the back up heating system) or be a separate pre-heat tank to a back up tank. Household hot water storage tanks typically range from about 150 - 450 litres. The capacity of storage designed into the system will depend on the hot water used by the household. Hot water use varies significantly from one household to another but a starting estimate is 75 litres per person.

Range of performance of the technology per unit installed:
In Canada, Approx 500-1000 Kwh/m²/year or approx 1.8 - 3.6 GJ/m2/year

Range of costs per unit of energy and per system (installed, and maintenance costs):
Residential domestic hot water (DHW) systems cost approx. $800-$1,400 per person, installed (2006 CAD) (http://www.bcsea.org/sustainableenergy/solarhotwater.asp). A household system for 2-4 people may cost from approx. $4,500 to $6,500.
Maintenance contracts may be purchased as part of installed cost or as required. Expect to pay local hourly plumbing rates. THE 2 SET OF NUMBERS DOESN'T MATCH: 800-1400/PERSON => 1600-2800/2 PERSONS => 3200-5600/4 PERSONS compared to 4500-6500

Design, Installation, Maintenance & Operation of SDHW:

Design of a SDHW:
Expertise/knowledge required can include: sizing the SDHW system, plumbing, electrical, mechanical, general construction.

Installation of a SDHW:
Expertise/knowledge required can include: plumbing, electrical, mechanical, general construction skills, roofing.

Maintenance of a SDHW:
Maintenance depends on type of system.
Expertise/knowledge required can include: plumbing, electrical, mechanical.
Tasks to be done can include:
  • Monitoring system pressure.
  • Replacement of anti-freeze solution after approx 7-10 years (for closed loop pressurized systems).
  • Repair or replacement of circulation pumps.

Operation of a SDHW:
Can be monitored and operated by homeowner with instruction from contractor/installer.

Training for designers and installers:
CanSIA is working with colleges to implement training programs for designers and installers of SDHW systems, based on the North American Board of Certified Energy Professionals SDHW certification. A wide variety of training opportunities exist from online courses and free information to hands on workshops and college courses. See www.cansia.ca for more information.

Range of Operational & Maintenance requirements (ex: how much labour time per week for how many people):
Requires only periodic monitoring and maintenance to ensure proper functioning.
Monitoring and Operation: 0.5 hr/month - 1 hr/year, 1 person
Maintenance: 1-2 hr/year, 1-2 person

Potential problems or challenges:
To ensure system performance:
Investigate certification of collectors or evacuative tubes. Two rating and certification systems are: The Solar Rating and Certification committee(SRCC) and Florida solar Energy center collector approval (FSEC).
A new program is in place to provide Canadian Standards Association certification (CSA F379-5) for solar hot water systems and systems in Canada are now able to apply for CSA certification.
Other considerations:
Investigate Maintenance contracts or warrantees.
Ensure system is designed for climate and hot water use.
Ensure southern exposure clear of obstructions between the hours of 10 AM and 3 PM or longer.

Permitting:
Many jurisdictions in Canada are still unfamiliar with solar hot water systems. New CSA system certification should help build confidence with decision makers and ease the permitting process. Contact your local permitting office early in project development to find out what permits may be required. Work with your local system retailers to provide decision makers in your area with information about solar hot water systems.

Range of warranties and life expectancy of the systems:
Warranties: 10 years
Life Expectancy: 20 - 30 years

Solar Resources Assessment:
Site specific solar resources can be measured by visual techniques and inspection or through commercially available solar site analysis tools. The U.S. National Renewable Energy Laboratory has extensive solar radiation resource information at http://rredc.nrel.gov/solar/. Links to Canadian solar radiation data can be found at http://www.canren.gc.ca/resou_asse/index.asp?CaId=55&PgId=452

Canadian Solar Resource maps are available at: http://atlas.nrcan.gc.ca/ and https://glfc.cfsnet.nfis.org/

Inputs and outputs for the technology:
Outputs:
Solar Thermal collectors directly convert energy from the sun to useable heat energy. Heat produced by the SDHW system can be used for heating water or space (see under "Potential combination …" for more details).

Inputs:
Sun:
A southern exposure unobstructed from the hours of 10 AM to 3 PM is preferred.

Anti-freeze solution and heat exchanger:
Many systems use an Anti-Freeze liquid (usually propylene glycol) and a heat exchanger to convert energy from the sun to useable heat energy. The anti-freeze solution usually lasts many years before having to be replaced.

Electricity:
Most systems have electric pumps that circulate propylene glycol through a pressurized closed loop. The amount of electricity required is minimal. It could be provided by the grid or by other sources such as a PV panel (see under "Potential combination …" for more detail).

Potential combination with other energy systems (hybrids and combination systems):
Water Heating and Space Heating:
SDHW is often combined with solar hot water space heating. The capacity of the system can be increased to provide space heating (through radiant floor/wall or baseboard hot water heaters) in addition to domestic hot water. (See SDHWheating link)

Photovoltaic (solar electric):
Most systems have electric pumps that circulate propylene glycol through a pressurized closed loop. The amount of electricity required is minimal. These electric pumps can be DC and run by a PV panel ensuring hot water production when there is no electrical grid.

Roofing Material and PV:
Some Solar Hot Water collectors are specifically designed to double as roofing material. If you need a new roof, this is a good time to consider solar hot water roofing collectors (or any solar roof mounted system). Some roofing solar hot water collectors integrate with Photovoltaic (solar electric) roofing materials and can be installed together to perform the function of shingles or other roofing materials. Offsetting the cost of roofing materials helps improve the cost effectiveness of the solar system.

Links to other sources of information:

Sources of supply (in Canada):

Check CanSIA's website for contact information for suppliers and installers in your area. www.cansia.ca
Énergie Solaire Québec sells for a small fee (free with membership) a list of renewable energy suppliers and businesses in Quebec. http://www.esq.qc.ca/

Recommendations on how to proceed with a project development:

Contact CanSIA: check their database for a local installer.
Find a contractor: As when hiring any contractor, ask for references from other clients or examples of their work and past experience.
Contact your local building inspector and municipal permitting office.
Ensure you have the necessary permits and the inspector is familiar with your plans before construction.
Check the links above for more information.
Check for local incentives, rebates, etc., to offset the cost of installation; local renewable energy associations such as CanSIA will be able to help with this.


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Created: 02-13-2008
Modified: 03-31-2008