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Solar
WaterHeating
A Buyer’s Guide
Systems
Natural ResourcesCanada
Ressources naturellesCanada
This digital mosaic of Canada, produced by Natural Resources Canada (Canada Centre for Remote Sensing), is a composite of individual satellite images. The differences in the density of vegetation are illustrated through shading.
To obtain additional copies of this or other free publications on energy efficiency, please contact:
Electricity Resources BranchRenewable and Electrical Energy DivisionNatural Resources Canada580 Booth Street 11th FloorOttawa, ON K1A 0E4
Toll-free: 1 877 722-6600
E-mail: [email protected]: www.nrcan.gc.ca/redi
Solar Water Heating Systems: A Buyer’s Guide
Prepared for Natural Resources Canada with the assistance of Michael Noble, EnerWorks, London, Ontario
Layout and design by Mantle & Overall Communications, Ottawa, Ontario
This guide is distributed for informational purposes only and does notnecessarily reflect the views of the Government of Canada nor consti-tute an endorsement of any commercial product or person. NeitherCanada nor its ministers, officers, employees or agents makes any warranty in respect of this guide or assumes any liability arising out of this guide.
© Her Majesty the Queen in Right of Canada, 2003
Cat. No.: M92-179/2000EISBN 0-662-28486-0
Aussi disponible en français sous le titre de : Les chauffe-eau solaires : Guide de l’acheteur
Recycled paper
About this Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
What are the benefits of a solar water heater? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
What is in a solar water heating system? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Will we always have hot water? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Is our house suitable for a solar water heater? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
What will a solar water heater do to the appearance of our house? . . . . . . . . . . . . . . . . . . . . . . . . . 5
What type of solar water heater should we buy? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
What do we need to know before we contact a dealer? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Do we need a year-round or a seasonal solar water heater? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6What are the available system sizes? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Where should the solar water heater be installed? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
How do we select a dealer? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Where do we find a dealer? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10What should be expected of the installer? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
What do we need to know to complete our own installation? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
What maintenance should we do? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
How can we further increase the energy savings? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
What other ways can solar energy improve the quality of the energy we use? . . . . . . . . . . . . . . . . 12
How does a solar water heater work? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Energy Collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Energy Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Energy Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Determining your energy savings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Table of yearly energy requirement for water heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Calculating your savings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Where can we find out more about solar energy? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Reader Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
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Table of Contents
About this Guide
This Guide has been prepared to assist consumers with the purchase of a solar water heater,also known as a Solar DomesticHot Water (SDHW) system, fortheir home. Some of the topicscovered in the Guide include:benefits of solar water heating,how a solar water heater works,selection of a product and dealer,installation and operation of asystem, and product and dealerselection. The Guide is not a“how to” manual on installing a solar water heater.
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What are the benefits of a solar water heater?Solar water heaters provide you with several benefits overconventional water heaters. You will reduce your hot waterheating costs. You will also bedirectly reducing greenhouse gas emissions (carbon dioxide,CO2, released into the atmos-phere), thereby contributing to a healthier environment.
The energy you can expect to saveby switching to a solar water heaterdepends on several factors such as the size of the collectors andstorage tank, appliance efficiency,amount of sunlight in your regionand, very importantly, the amountof water you use. A typical solarhot water system will reduce annu-al energy costs by 40 to 50 percent.You can expect that a solar waterheater will provide you with 1500to 3000 kWh of energy per year,depending on your hot water usageand regional climate. The map on page 4 shows approximate energy savings for various places in Canada.
Domestic water heating contributesapproximately 6 million tonnes of CO2 each year toward Canada’sgreenhouse gas emissions. Byinstalling a solar water heater, youcan make a difference. In fact, asolar water heater will eliminate up to 2 tonnes of CO2 emissionsper year, in proportion to yourenergy savings.
3
Benefits of a solar water heater
0
100
200
300
400
500
Solar energy (kWh) Back-up Energy (kWh)
Dec.Nov.Oct.Sept.Aug.JulyJuneMayAprilMarchFeb.Jan.
Example of Annual Solar Energy Contribution
Most solar water heaters consistof solar collectors mounted onthe roof of a house; a pump forcirculating the heat transfer fluid;a heat exchanger for transferringthe heat to storage; and one ortwo storage tanks for storingsolar-heated water for periodswhen there is no sun.
For more details on how energy isproduced, see the section entitledHow does a solar water heater work?on page 13.
Will we alwayshave hot water?Modern solar water heaters arewell suited for the Canadian climate because they produce energy when the outside tempera-ture is well below freezing. Theyalso have mechanisms that protectthem from freezing in the winterand from overheating on hotsunny days. Nearly all systems use the existing water heater as a backup energy supply toensure that there is always a supply of hot water.
Is our house suit-able for a solarwater heater?Most solar water heaters can easilybe retrofitted to your existingwater heater. Inside your home,you will need a small space adja-cent to your existing water heaterfor the solar-heated water storagetank and the heat transfer unitthat is connected to the collectors.Having a storage tank for yoursolar-heated system will reduce thelikelihood that you will run out of
4
What is in a solar water heating system?
36%Prince George
43%Vancouver
39%Victoria
43%Kamloops
18%Resolute
26%Inuvik
26%Baker Lake
25%Iqaluit
46%Winnipeg
44%Thunder Bay
42%Muskoka
38%Timmins
42%North Bay45%
Sault Ste Marie
45%London
45%Toronto
45%Ottawa
44%Montreal
41%Quebec City
39%Charlottetown
41%Halifax
30%St. John‘s
48%Calgary
53%Medecine Hat
48%Saskatoon
49%Regina
31%Whitehorse
21%Sachs Harbour
41%The Pas
45%Edmonton
43%St. John
Potential portion of water heating energy savings obtained by installing a solar water heater. Figures assume a freeze-protectedsystem with 6 m2 of single glazed flat plate solar collectors and two 270 litre (60 gallon) hot water tanks. Simulations werecompleted with WATSUN 13.2 software, and use local climate data.
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hot water in your home. However,most small systems, for examplesystems with 3 m2 of collectors, do not come with a storage tank.
The best location for the collec-tors is on an unshaded, south-facing roof or wall. For excellentperformance, solar collectorsshould face due south and be set at an angle of 18°–50° fromthe horizontal plane. Collectorscan also be mounted on a sturdyframe near your home, or can be integrated into the roof of a storage shed. The solar collectors typically require a flat mounting area of about 3 m2 for each collector. Mostinstallations require one to two solar collectors.
A small path is required for thepiping which connects the solarcollectors to the storage unit. Thepiping usually can be installedthrough closets, cold air returns,wall cavities, and along the outside wall of the home.
What will a solar waterheater do to the appearance of our house?Components for solar waterheaters are located outside and inside your home. Properlyinstalled solar water heaters will not detract from your home’s appearance or disruptyour normal household routines.
Taking a small amount of time to examine the different possiblelocations for the solar collectorarray can make a large differenceon the visual appeal of the final
installation. On the outside of yourhome, the largestvisible component is the solar collectorarray. Solar collec-tors look similar to low-profile sky-lights. Modern solarcollectors are usuallyfinished in anattractive aluminumcasing with a glasscover. Collectors are 10 to 15 cm in thickness andrequire a flat area of about 3 m2 each.
Special frames toraise the collectoroff the roof areusually not desirable and, inmost cases, the improved performance of the system maynot justify the additional cost. On the other hand, installing the solar collector at a shallowangle may compromise winterperformance and will not assist in snow removal. Mounting the collector flush with the roofcontributes to a neat installationand ensures the collector will notcontribute to additional wind or snow loading.
The only other part of a solarwater heater that may be visibleon the outside of your house isthe insulated piping connectingthe solar collectors with the solarstorage unit. A good installationwill pass this tubing through a special roof flashing in an unobtrusive place. Sometimescathedral ceilings or special wall construction require that
the piping be run along the outside of the house to a moreconvenient entry point. In this case, a downspout can beinstalled to hide the piping, toavoid any negative impact on the appearance of the house.
5
Glazed flat plate collectors installed on a Nova Scotia home.
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Solar water heater dealers areequipped to provide you withinformation on currently avail-able models. They will advise you in selecting the best modelfor your needs and help select asuitable location for the system.In most cases, dealers can alsooffer complete installation ser-vices. Before contacting a dealer,however, you should becomefamiliar with the various types of solar water heaters and theirsuitability for your needs.
A variety of solar water heaterdesigns are available for con-sumers. There are variations incollector styles and componentarrangements, as well as differentmethods of freeze and over-heating protection.
If you are planning to use a solarwater heater year-round in Canada,it must be protected from freezingin the winter and overheating inthe summer. Solar water heatersthat meet the Canadian StandardsAssociation (CSA) Internationalguidelines have automatic controlsto prevent overcharging the solarheater (i.e. to prevent potentialscalding water temperatures). Thefollowing are common systemtypes (the first two can be freeze-protected in the Canadian climate):
• “Antifreeze” systems use special fluid to transfer heatfrom the collector to a heatexchanger in the storage unit.These systems are fully freeze-protected, prevent contamina-tion of the hot water, and canoperate in all climate condi-tions. Snow will slide off thecollector as the sun begins to warm them. On days with
heavy snowfall, performancecan be increased by removing the snow off the collectors.
• Drainback systems auto-matically drain the collectorswhen they are not collectingsolar energy or when the temperature of circulatingwater is 3°C or less. Make surethat the system’s minimumtemperature rating is appro-priate for your climate.
• Thermosiphon systems do not have freeze-protection, andare popular for cottages wherewater heating is needed only inthe summer. These solar waterheaters are often less expensive than models incorporatingfreeze-protection.
What do we needto know beforewe contact adealer?Before meeting with your dealer, you should review the following questions.
Do we need a year-round or a seasonal solar water heater? This depends on when you will beusing the residence where the solarheater is installed. Year-round solarwater heaters can withstand theextremely cold temperatures oftenexperienced in Canada. These typesare recommended if the residence is used throughout the year, and is in a climate requiring freeze-protection. Seasonal solar waterheaters are designed for use in climate conditions not requiringfreeze-protection. Seasonal solarwater heaters tend to be less
expensive than solar water heaterssold for year-round use becausethey do not require equipment to protect the solar collectors and outside piping from extremefreezing temperatures.
Year-round solar water heatersYear-round solar water heaters aremore convenient and fail-safe be-cause they can operate in all climateconditions. Because these solarwater heaters operate all year, theynormally provide more solar hotwater than a seasonal water heater.These products require maintenancecomparable to conventional waterheaters. Maintenance will ensuregood performance and increaseyour energy savings.
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What type of solar water heater should we buy?
Thermosiphon solar water heater atCamp Queen Elizabeth, BeausoleilIsland on Georgian Bay, Ontario.Courtesy of Solcan Ltd.
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Seasonal solar water heatersIf your family does not use the residence during the wintertime,you should consider buying a seasonal solar water heater.Seasonal solar water heaters are ideal for summer vacationhomes, and for warmer regionsnot requiring freeze protection.Ideally, they are designed for useonly during the spring, summerand fall. For cottage use, a seasonalunit with a safe low temperaturerating of 5°C or 0°C is usually adequate. For residential use, a sea-sonal unit with a safe low temper-ature rating of 0°C or -10°C shouldbe chosen. In some West Coastcommunities, a -10°C seasonalsolar water heater can be used all year, but in most parts of thecountry it can only be used forabout eight months of the year.Good examples of seasonal solarheaters are batch heaters or inte-gral collector-storage systems.Seasonal solar water heaters must be shut down and drainedwhen the temperature drops below the water heater’s safe lowtemperature rating.
What are the available system sizes?The easiest way to determine theoptimum size for a solar waterheater is to match the size to the number of occupants in thehome and their water use. Aswell, consider planning for theneeds of future occupants. Theaverage hot water usage for yourhouse will also depend on thenumber of appliances requiringsubstantial amounts of hot watersuch as dishwashers, washingmachines, whirlpools or hot tubs.
A solar water heater usuallycomes in three standard sizes and corresponds to your daily hotwater use: 150 L/day; 225 L/day;and 300 L/day (See Table of YearlyEnergy Requirement for WaterHeating on page 15 to determinethe system size you will need).These sizes vary according to thevolumes of hot water the heatersare designed to deliver on anaverage day and are not a ratingof their maximum output.
Where should the solar water heater be installed?Your solar water heater dealer willhave the expertise to provide youwith proper site and installationrecommendations. However,before making your final decision,look at your options. Take intoaccount the appearance of the col-lectors in each possible location.
Ideally, the mounting locationshould remain unshaded for at least 80 percent of the timebetween 9:00 a.m. and 3:00 p.m.during the winter and summer.For seasonal units, only the sum-mer period is critical. Shading cancome from your own house, fromtrees or shrubs on your property,and from neighbouring buildingsand trees. If the solar water heateris to be used during the wintermonths, take into account thatthe shadows are longer during the winter months, because of the lower position of the sun. At noontime during the wintermonths, a six metre high tree orbuilding can produce a shadow of ten metres or more, which cansignificantly shade a collectormounted on the ground or a wall.It is also important to note that
in most Canadian municipalitiesthere are no laws that prevent a neighbour from building orplanting something that couldshade your collectors.
7
Small systems often come with aheat exchanger and a combinedsolar preheat and auxiliary tank.
Most medium to large systemshave both an auxiliary tank and a solar preheat tank with a heat exchanger.
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A suitable roof or wall locationshould be about 6 m2 in area andshould face between southeast and southwest. In most of Canada,excellent performance can beobtained with collectors that aremounted between 18° and 50°from the horizontal. Most roofshave a minimum slope of 18° andare usually the preferred locationfor solar collectors. If no suitableroof or wall location is available,then a ground-mounting frame isrecommended. Snow coverage andthe seasonal changes in the sun’sposition should be considered foryear-round installations.
To reduce heat loss, all mountinglocations should allow the con-necting insulated collector pipesto pass through the roof or wall,preferably at a point adjacent tothe collector. The pipes should be able to pass unseen throughclosets, walls or floor spaces, to the basement or hot waterplumbing area. Piping bundlesmounted on the exterior of thehouse should be protected in asleeve such as a downspout. Thiswill protect the insulation fromultraviolet degradation, decreaseheat losses, and ensure the instal-lation does not detract from the
appearance of the house. Somesystems use piping that combinesthe supply and return lines and sensor wire into one bundle,thereby making installation much easier.
8
6 metres
10 metres
The sun is much lower in the winter than in the summer. Therefore, a six-metre tree or building can significantly shade a collector mounted on the ground or on a roof, even at a distance of 10 metres.
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Finally, check that there are no zoning restrictions in yourcommunity that might restrictthe placement of solar collectors.Some areas might also require a building permit. Your installershould be able to assist you with these issues.
9
Solar collectors should be positioned facing southeast to southwest.
t
SW
Solar collectors should be installed on asoutheast to southwest orientation for maximumperformance.
For best performanceinstall collectors at an angle between
18°–50°from the
horizontal plane.
SE
A good dealer will help you selecta solar water heater that meetsyour specific needs. The dealershould provide all necessary oper-ating information, explain main-tenance requirements, and in thecase of seasonal water heaters, theoperating temperature limits. Ifyou plan to complete your owninstallation, the dealer shouldsupply you with well-documentedinstructions and fully explain thesystem’s warranty.
If possible, restrict yourself todealers who can offer a warrantyon both parts and labour andwho have a successful trackrecord of satisfied customers. If possible, ask to view a solarwater heater installed by the dealer in your community.
Consultation with a dealer shouldinclude a visit to your home so the dealer can make an accurateestimate of the installation costand help you make the final deci-sion on where the collectors andthe storage unit should be placed.
When choosing a solar waterheater to meet your basic require-ments, consider the following:• year-round or seasonal use;• best placement of the solar
collector array; and,• size of the system.
Choose a solar water heater that:• meets current CSA standards
or will be approved by yourlocal building inspector;
• has warranty coverage; and,• has support from a local
dealer or installer.
Your purchase should include the same considerations as those involved in purchasing any new appliance:• consider the dealer’s reputa-
tion and experience;• examine the limitations
of the warranty;• ask for photos or to view
completed installations;• inquire about follow-up
service arrangements;• review all contracts and
agreements; and,• obtain more than one
written estimate.
Where do we find a dealer? There are several resources you can use to assist in finding a dealer to meet your needs. The Canadian Solar IndustriesAssociation and the Solar EnergySociety of Canada, Inc., bothmaintain databases on dealersand manufacturers in your area.Both of these organizations canbe accessed through the Internet;details on how to find them are provided under the section Where can we find out more aboutsolar energy? on page 18.
What should be expected of the installer?The Canadian Solar IndustriesAssociation (CanSIA) maintains alist of solar water heater installers.It is highly recommended thatyou have your solar water heaterinstalled by an experiencedinstaller recognized by CanSIA.
When you have identified a dealer, ensure that the contractdocuments the terms of theinstallation and that all appro-
priate permits are obtained fromlocal authorities. The contractshould require the installer tostart up the water heater, demon-strate to you that it is working asdesigned, and show you how toperiodically check its operation.
In addition, before the installerleaves, you should go through the following checklist:
• You are fully satisfied that the solar water heater hasbeen properly installed andthat you fully understandhow the appliance works.
• The installer has provided a signed checklist verifyingthat the installation has beenchecked for plumbing leaks,that roof and wall pipe pene-trations are properly sealed,and that outside pipe insula-tion is properly jacketed andsealed against the weather.
• You have an owner’s manual.
You should understand:• how to shut down, isolate
and drain the water heater in an emergency;
• how to check that the waterheater is operating properly;
• how to drain a seasonal waterheater in the fall and refill it before starting it up in the spring;
• how to carry out any routinemaintenance, such as toppingup fluid reservoirs;
• when to call a qualified solartechnician to check or replaceantifreeze; and,
• details of any warranty covering the installation.
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How do we select a dealer?
What do we need to know to complete our own installation?The cost of installing a solar water heater can be reduced ifconsumers carry out some of the work themselves. Installing asolar water heater that will deliverreliable performance (consistentwith the performance rating)requires some experience in elec-trical, plumbing, and carpentry. It is important to complete theinstallation to CSA standards.Some specialized knowledge isrequired to mount solar collec-tors, prime the collector piping,install control sensors, and adjustthe water heater. You should dis-cuss the warranty limitations fordo-it-yourself installations withyour dealer. You are also responsi-ble for meeting local building regulations and electrical andplumbing codes.
What mainte-nance should we do?Routine checks and maintenancewill ensure your savings are consistent.
Once your solar water heater isproducing hot water, a monthlycheck-up is recommended. Thereare three easy ways to verify thatyour system is running well:
1. Look to see that the pump is operating when it is sunny.
2. Check carefully that the pipes are warm.
3. Review your energy bills to confirm your savings.
To ensure the water heater is collecting solar energy when thechecks are made, complete thechecks on a sunny day just afteryou use some hot water. Be care-ful, the pipes can be very hot!Maintenance of a solar waterheater should be carried outaccording to the manufacturer’srecommendations. Your solarwater heater is an appliance. It should be maintained on a regular basis, like your other heat-ing and cooling systems. If youhave an antifreeze system, theantifreeze should also be checkedevery 1 to 2 years according tothe manufacturer’s recommenda-tions. As well, if you carry outyour own maintenance, ensurethat the manufacturer’s mainte-nance practices are followed, andthat you use only recommendedantifreeze for topping up orreplacement.
You should ask your dealer forprocedures to follow when youwill not be using your solar water heater for extended periods of time. If you suspect a mal-function, contact your solar water heater dealer immediately.
How can we fur-ther increase theenergy savings?By timing your heavy hot waterusage, you can increase the ener-gy savings from your solar waterheater. For example, by washingyour clothes early in the day,between 9:00 a.m. to 3:00 p.m.,you can maximize the energy savings benefits of your solarwater heater. As well, you willgive the system a chance to re-charge during the rest of the day.
You can also introduce some simple conservation measuresthat will reduce your water heating bill, such as: • installing low-flow
shower heads;• adding an insulating jacket
to the hot water tank if it isnot a high efficiency tank;
• insulating all hot water pipes;• setting your back-up heater
temperature to 50°C;• changing washers in
leaky faucets;• using lower water temper-
atures for laundry; and,• installing a separate hot
water temperature booster on your dishwasher.
11
Completing your own installation
What other wayscan solar energyimprove the qual-ity of the energywe use?Solar pool water heating is a common use of solar energy.Unglazed plastic collectors areused to heat the pool water, sub-stantially reducing energy costs.Solar water heaters can be lessexpensive than gas pool heaters.Natural gas or electricity heatsapproximately one third of all residential pools.
Passive solar heating incor-porates the use of solar energyinto the architectural design andselection of building materials,such as windows, to maximizethe benefits of solar radiation.
Active solar heating can also be used to heat floors or the space of buildings. Applications includeradiant floor heating and solar air heating systems, such as theSolarwall®, which preheats venti-lation air to reduce heating costsand improve air circulation.
Photovoltaic systems convertthe sun’s energy into useable electricity. These systems are now being used to supply theelectrical needs of residences thatare separated from the electrical grid. Some homeowners also use photovoltaic modules to reducedependence on utilities withingrid-serviced areas.
12
Unglazed solar collectors are commonly used to heat residential pools. Courtesy of Taylor Munro Energy Systems Inc.
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Solar water heaters perform threebasic operations before the hotwater comes out of your tap:
1. Energy Collection:Sunlight is collected andconverted to heat energy.The solar collector is mounted onor near your home facing south.As the sunlight passes throughthe collector’s glazing, it strikesan absorbing material. This mate-rial converts the sunlight intoheat, and the glazing prevents theheat from escaping in a similarmanner to leaving a car parked in the sun with its windowsrolled up. The temperature insidea glazed solar collector on yourroof can easily reach 150°C whenthere is no heat transfer fluidflowing through it.
The two most common types of solar collectors used in solarwater heaters are glazed flat plateand evacuated tube collectors. Aglazed flat plate collector consistsof a shallow rectangular box witha transparent glass “window” covering a flat black plate. Theblack plate is attached to a seriesof parallel tubes or one serpentinetube through which air, water, or other heat transfer fluids pass.
An evacuated tube collector consists of several individual glass tubes, each containing ablack metal pipe through whichthe heat transfer fluid passes. The space between the pipe andthe glass tube is “evacuated,” so the air is removed.
Although uncommon, unglazedplastic collectors can be used as a seasonal solar water heatingsystem. However, they are usedmostly for pool heating.
Each collector has its advantages,and each can perform well if matched with the proper, well-designed, storage unit.
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How does a solar water heater work?
Cutaway view showing glazed flat plate solar collector components1. Metallic Absorber 2. Glazing 3. Housing 4. Insulation 5. Heat transfer fluid inlet
tSunlight
Hot Fluid TrappedHeat
In a flat plate collector, sunlight is converted to heat and trapped by the “greenhouse effect”.
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2
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54
2. Energy Transfer:Circulating fluids transferthe collected energy in the form of heat to a storage tank.Heat energy is transferred fromthe collector to the water storagetank. In some water heaters, hot fluid is pumped from the collector to the storage tank. Thepump is powered by electricitythat either comes from an electri-cal wall outlet or a small photo-voltaic module located beside the collector.
In other types of solar waterheaters, the sun heats the storagetank directly, so the fluid in the collector is heated and risesnaturally to a storage tank abovethe collector. This type of solarwater heater is often referred to as a thermosiphon system. It does not require an electricpump. Passive solar and solarphotovoltaic-powered systemswill continue to operate even if there is a power outage. Theproducts that require electricityfrom a wall outlet will not operate during a power outage.
3. Energy StorageSolar-heated water is stored in an insulated tank until you needit. Hot water is drawn off the tank when tap water is used, and cold make-up water enters at the bottom of the tank.
Solar water heaters tend to have a slightly larger hot water storagecapacity than conventional waterheaters. This is because solar heatis available only during the dayand sufficient hot water must be collected to meet evening and morning requirements.
14
Follow steps 1-5 to translatethese energy contributionsinto dollar savings:
Step 1 Estimate your annual energyrequirement for hot water heatingfrom the table below. Read off theenergy requirement of electricity,litres of oil or propane, or cubicmetres of natural gas, dependingon the fuel you use for heatingyour water. Write this value inBox 1.
Step 2 Find your (or one with a similarclimate) location or the nearestlocation to you on the map ofCanada on page 4. Write the percentage that corresponds tothe potential portion of waterheating energy saved in Box 2.
Step 3 Multiply Box 1 by Box 2. Writethis figure in Box 3, which is yourestimated energy saving in kWh,litres, or cubic metres.
Step 4 On a recent electricity, gas, oil or propane utility bill find theamount you paid and the amountof kWh, litres, or cubic metres of fuel used. If you are paying a fixed monthly rate, call your utility company for this infor-mation. Write the amount youpaid in Box 4 and the amount of fuel used in Box 5.
Step 5Multiply Box 3 by Box 4 and divideby Box 5. This is your estimatedannual dollar savings from yoursolar water heating system.
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Determining your energy savings
Table of Yearly Energy Requirement for Water HeatingHousehold Size (in persons) 2 3-4 More than 5
Average Hot Water Usage 150 litres/day 225 litres/day 300 litres/day
Suggested Solar Water Small Medium LargeHeater System Size • no pre-heat tank • pre-heat tank • pre-heat tank
• about 3 m2 • 5-6 m2 • greater than 6 m2
Equivalent? Existing Water Heater Tank Size 180 litres 270 litres 270 litres
(40 gallon) (60 gallon) high power output (60 gallon)
Estimated Annual Energy Required by Fuel Type
Electricity kWh 3400 5000 6600
Natural Gas (m3) 500 740 1000
Oil (litres) 480 720 960
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Box 1Yearly energyrequirementfor water heatingin kWh, m3, or litres
Example:5000 kWh
Your figure
Box 2Portion ofenergy met by a solar water heatingsystem in your region(see map on page 4)
Example:47/100
Your figure
Box 3Potential energy savingsby a solarwater heatingsystem in kWh, m3, or litres
Example:2350 kWh
Your figure
Box 4Dollars paid for energy used (from a recent utility bill)
Example:$55
Your figure
Box 5Amount ofenergy used in kWh, m3, or litres (from a recent utility bill)
Example:600
Your figure
AnswerEstimatedannual savingsfrom a solarwater heatingsystem
Example:$215
Your figure
Calculating your Savings
x = x ÷ =
Gigajoule (GJ): Unit of energyequal to 1,000 million joules,950,000 BTUs, 278 kWh of electricity, 25.8 litres of oil, 26.9 m3 of natural gas, or 39.2 litres of propane.
Solar photovoltaic panel:A group of modules fastenedtogether. The modules are madeup of cells that convert lightdirectly into electricity. The term “panel” is often used interchangeably with the term “module”.
Pre-heat system: Describes an add-on solar water heater,which can be installed with a conventional water heater.
Safe low temperature ratingor minimum operating temperature rating: Outsidetemperature that defines thelower limit for freeze-protectionof the solar water heater.
Solar collector: A device thatabsorbs solar energy and convertsit into useable heat.
Solar contribution: Amount of solar energy that a solar waterheater converts into hot water on an average day.
Solar Domestic Hot Water(SDHW) system: Describes astand-alone residential solar waterheater that is installed with a conventional water heater. It isalso a name sometimes used bysolar specialists for a residentialsolar water heater.
Solar fraction: Percentage of the total water heating load provided by the solar water heater.
Storage unit: Tank or vesselthat stores the solar-heated water.Some systems have only a singletank, and use the same tank forstoring solar-heated water andwater heated with auxiliary energy. Other systems use twoseparate tanks for storing solar-heated water and water heatedwith auxiliary energy.
17
Glossary
Natural Resources Canada(NRCan)Renewable and Electrical EnergyDivision Energy Resources Branch580 Booth Street, 17th FloorOttawa, OntarioK1A 0E4Fax: (613) 995-0087Web site:http://www.nrcan.gc.ca/redi
or
Natural Resources CanadaCANMETEnergy Technology Branch580 Booth Street, 13th FloorOttawa, OntarioK1A 0E4Fax: (613) 996-9418Web site:http://www.nrcan.gc.ca/es/etb
Canadian Solar IndustriesAssociation (CanSIA)2415 Holly Lane, Suite 250 Ottawa, OntarioK1V 7P2 Tel: (613) 736-9077Fax: (613) 736-8938Web site: http://www.cansia.ca
Énergie solaire Québec460, rue Sainte-Catherine ouest,Bureau 701Montréal, QuébecH3B 1A7Tel: (514) 392-0095Fax: (514) 392-0952Web site: http://www.esq.qc.ca
To order additional copies of this publication and other publications on renewable energy and energy efficiency call our toll free line at 1-800-387-2000. You can also obtain a copy of this publica-tion by visiting our web site athttp://www.nrcan.gc.ca/redi
For more information on solarwater heating systems or othertypes of renewable energy tech-nologies, visit NRCan's CanadianRenewable Energy Network(CanREN) Web site athttp://www.canren.gc.ca
Free software available to assist you in your decision.Renewable energy technologies,such as a solar water heating sys-tem, can be a smart investment.RETScreen® International justmade it easier. RETScreen®International is a standardizedrenewable energy project analysissoftware that could help youdetermine whether a solar waterheater is a good investment foryou. The software uses Microsoft®Excel spreadsheets, and a com-prehensive user manual and supporting databases to help your evaluation. The software anduser manual can be downloadedfree from the following web site:http://www.retscreen.gc.ca or by contacting NRCan by phone at (450) 652-4621 or by fax at (450) 652-5177.
18
Where can we find out more about solar energy?
19
Reader Survey
Thank you for your interest in NRCan’s Solar Water Heating Systems: A Buyer’s Guide.
To improve this guide we would like to ask you to take a few moments to answer some questions.
Where did you receive your copy of the Buyer’s Guide?
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