Build Your Own Solar Water Heater
If it feels warm to the touch, that means heat is leaching out, and instead of warming your water, it's warming the air uselessly. So wrap an insulating blanket around your water heater. The payback will be around two years. Head to Chapter 11 for other things you can do to increase the efficiency of your water heater and a plethora of other home appliances.
The water heater accounts for about 20 percent of the typical home's power budget. Dishwashers and washing machines use up to 80 percent of their energy on heating water, and only 20 percent running the mechanical equipment. The cost of taking showers and baths is almost entirely in the cost of heating water. Unfortunately, the typical domestic water heater is wasteful. It holds a considerable amount of hot water, and when it's not being used, heat seeps out of the tank, which is sheer inefficiency. The best water heaters have thick insulation, but some heat is still lost.
Many test procedures have been proposed by various organizations to determine the thermal performance of solar water heaters. Testing of the complete system may serve a number of purposes. The main one is the prediction of the system's long-term thermal performance. System testing may also be used as a diagnostic tool to identify failure and causes of failure in system performance. other purposes include the determination of the change in performance as a result of operation under different weather conditions or with a different load profile. A total of five international standards on solar domestic water heater performance testing have been published Solar Water Heater Performance Evaluation 305 The test methods in this standard define procedures for the indoor testing of solar water heaters with a solar simulator. The characteristics of the solar simulator are defined in ISO 9845-1 1992 (see Chapter 4, Section 4.1.3). The entire test sequence usually takes 3-5 days and the result is...
The performance of thermosiphon solar water heaters has been studied extensively, both experimentally and analytically, by numerous researchers. Among the first studies were those of Close (1962) and Gupta and Garg (1968), who developed one of the first models for the thermal performance of a natural circulation solar water heater with no load. They represented solar radiation and Ong performed two studies (1974 1976) to evaluate the thermal performance of a solar water heater. He instrumented a relatively small system with five thermocouples on the bottom surface of the water tubes and six thermocouples on the bottom surface of the collector plate. A total of six thermocouples were inserted into the storage tank and a dye tracer mass flowmeter was employed. Ong's studies appear to be the first detailed ones on a thermosiphonic system. Morrison and Braun (1985) studied the modeling and operation characteristics of thermosiphon solar water heaters with vertical or horizontal storage...
Most North Americans (almost 55 percent) heat their water with natural gas. About 38 percent heat water with electricity. (The few others heat with oil and liquid petro gas.) However, two types of water heaters are increasingly being used for their energy efficiency solar and tankless water heaters. I Solar water heaters are the best from an energy-efficiency standpoint, but the economics vary greatly from region to region and depend on your power rates and rate structure. From a pollution perspective, you can't do better than solar. See Chapter 16 for details. I Tankless water heaters have no storage tank they heat water as it is being used. They are generally gas-powered because of the need for very high, instantaneous power. They're more expensive than conventional water heaters, but if you don't use much hot water, you can save big in the long run. Tankless water heaters are especially good if you have a cabin or second home that you don't use that often. In this case, you won't...
Solar water heaters, when properly designed and installed, are great investments. Most people can afford a few thousand dollars for a solar water heater system without taking out loans. You can find do-it-yourself kits that work with existing water heaters, so you can keep your investment down in that way as well. A big benefit of a solar water heater is that you never need to conserve on hot water, regardless of how high energy rates go. From a pollution standpoint, water heating typically comprises around 18 percent of your power bill, so you can save exactly that much from your carbon footprint. If you are on a tiered rate structure, a solar water heater cuts into the most expensive part of your power bill first. For example, if you save 18 percent of the electrical energy you use, you may be able to save closer to 30 percent of your total power bill (see Chapter 5 for more details). PV systems are more popular than solar water heaters, but new plastics have been developed that are...
If your energy utility uses a tiered rate structure and you put in the solar water heater, your cost savings can easily be twice as much. Payback is therefore half as long. The solar water heater example offsets 18 percent of the household energy use, but in a typical tiered rate system, this accounts for closer to 35 percent of the total dollar cost in the utility bill.
If you choose a water heater with a tank, you should probably buy the largest one available. That sounds like strange advice, but it makes sense. Because larger tanks hold more water, the greater mass of the tank's contents will help maintain the temperature. More importantly, larger tanks often have thicker insulation and longer warranties. For a tankless model, consider how much hot water you need each day, how much you need at any one time, and whether the water heater is for part of the house or all of it. According to manufacturers, tankless water heaters are about 30 percent more efficient than water heaters with tanks in households that use no more than 40 gallons of hot water each day. Households that use twice as much water will get about half as much improvement.
Suppose that energy costs rise 12 percent per year instead of staying flat. If you put in the solar water heater, each year your savings grow. If you save 26 per month the first year, as in the earlier example, the next year your savings will grow to 30.24 per month ( 27 x 1.12). Then 33.87 ( 30.24 x 1.12), then 37.93, then 42.48, and so on. In this case, the payback is 44 months, down from 52 months.
The case of most energy-efficiency improvements, you have to invest cash before you see a single dime of savings. Payback is measured in months, or even years. Here's an example. You invest 2,000 in an on-demand water heater, which saves 30 a month in electric costs. Dividing 2,000 by 30 equals 67 months, or about 5 2 years.
Change the heating elements in your electric water heater every few years (most of them have two elements, one on top and one on bottom). Use a stainless steel heater element if your old one is corroded. This makes the unit operate more efficiently and avoids untimely failures.
Electricity is a ubiquitous part of our lives. We use it all of the time every day, from the electric alarm clock that gets us up to the television that provides the weather reports to the light we turn out at night as we slip off to sleep. The smoke alarm, water heater, and refrigerator all use electricity (in varying amounts) around the clock. As anyone who has lived through an extended electrical outage over many days will testify, we never realize how critical electricity is to our daily lives until it is gone.
Aside from your HVAC system (which I cover in detail in Chapter 8), appliances consume the lion's share of power in your home. Some of the biggest culprits in most homes are water heaters, washers and dryers, and refrigerators, which are on all the time. There are exceptions, of course. Some homes have aquariums that collectively steal the spotlight. Other homes have an old freezer in the garage that cranks the kilowatts 24 7. Increasingly common are homes with large entertainment centers, and these can gobble kilowatts with the biggest and baddest of energy pigs. You can determine your own annual usage and cost by gathering your electric bills, which show kWh used and your rate (see the next section for details). If your rate is higher or lower than 15 cents, adjust it accordingly. If you use gas or propane for your dryer, water heater, or stove, the annual cost will be around the same as for electric. Domestic water heater Unfortunately, the device doesn't work for 220VAC appliances...
As homeowners turn on lights and appliances hydrogen would be admitted to the fuel-cell, where it would recombine with oxygen drawn from the atmosphere to generate electricity and pure water. Pure water would be stored in a glass-lined tank for drinking, bathing and cooking. The two water tanks, as well as hydrogen tank, pumps, electrolyzer and fuel-cell, would occupy about the same space as a conventional water heater and furnace. Additional water, supplying the pool, hot tubs and landscaping would be available from wells one per block. tion or microwave. The homes would require perhaps a tenth of the water and a third of the energy now required, and they wouldn't need furnaces, water heaters and air conditioners.
An active solar water heater consists of a solar collector(s), a hot water storage tank(s), and a pump. In addition, a heat exchanger and expansion tank are required in freezing winter climates and an electrical generation device is needed if regular AC grid-connected power is not available. Piping, insulation, valves and fittings are considered installation materials and are normally available at hardware stores and plumbing centres.
Contract with a bottled water company. A bottled water company will rent you a dispenser and come out twice a month to refill it with a big jug of distilled or filtered water and do the regular maintenance. The cost is around 8 per month. You can get dispensers that will heat the water, which is more efficient than using your water heater but less efficient than using your microwave.
Solar energy, on the other hand, can't be stored, so it must be converted into a different form in order to be stored. Solar power can be stored as heat, which is how a solar domestic hot water heater works. Or it can be converted into electricity and fed into a battery, which then converts the electrical energy into chemical energy. When the energy is to be used, later that night or the next morning, the chemical energy is then converted back into electrical energy, which is fed into an appliance. This whole chain process is extremely inefficient because each step in the process is inefficient and the inefficiencies only multiply.
A special water heater tank incorporating a heat exchanger is used with one or more flat plate, roof-mounted collectors. Glycol, or some equivalent antifreeze fluid, fills the collector and routing pipes. A controller measures the temperature in the collector fluid, as well as the temperature in the hot water tank. When heat is available for transfer, pumps are activated to move the collector fluid.
I Changing habits With some energy-efficiency equipment, you have to change your consumption habits to take best advantage of the potential. For instance, if you install a solar hot water heater, taking showers in the late afternoon is better than taking them early in the morning. How willing are you to make the changes Furthermore, with some energy-efficiency investments, the only requirement is to change habits no cash is invested at all. An example of this is taking shorter showers.
You may be able to demand that some improvements be done before you buy an existing home. Perhaps you can get a seller to install some solar or other ir ll energy-efficiency equipment as a condition of sale. If a water heater is shot, perhaps you can demand a solar water heating system be put in its place, for example.
The line last night at the only Mickey D's still able to serve up burgers was brutal. The land-line phones in the house have been down since the storm blew through because they are all remotes that require an electrical connection. You've resorted to burning gasoline in your car to keep the cell phone charged up and your body cool, but you are wondering if you can refill the automobile's tank because half the local stations can't run their pumps. You're taking quick showers, careful to use as little hot water as possible, knowing that the water heater's controls are also electronic and don't work without power.
A schematic diagram of a direct circulation system is shown in Figure 5.9. In this system, a pump is used to circulate potable water from storage to the collectors when there is enough available solar energy to increase its temperature and then return the heated water to the storage tank until it is needed. Because a pump is used to circulate the water, the collectors can be mounted either above or below the storage tank. Direct circulation systems often use a single storage tank equipped with an auxiliary water heater, but two-tank storage systems can also be used. An important feature of this configuration is the spring-loaded
Completed in the fall of 2006, the Tahoe Center for Environmental Sciences houses classrooms and laboratories for programs that focus on understanding and protecting fragile alpine lakes. The three-story, 47,000-square-feet facility cost 25 million and is used by Sierra Nevada College, the University of California at Davis, the Desert Research Institute, and the University of Nevada, Reno. The facility uses 60 percent less energy and 30 percent less water than a comparable building. A variety of mechanical designs were used including chilled beams, displacement ventilation, radiant floor heating, overhead radiant heating and cooling panels, a turbine with cogeneration, lab exhaust heat recovery, 30-kW of building-integrated photo-voltaics, nighttime chilled water production with a cooling tower and 50,000 gallons of chilled water storage, direct evaporative cooling in air handlers and a demonstration solar hot water heater. Water-free urinals and low-flow toilets were installed in the...
Homeowners, therefore, are generally advised that they can expect no more than 50 to 70 of their DHW, i.e. non-space heating needs to be supplied by individual installations, and that they should fit a more reliable standby water heater. This could, of course, use zero or low carbon energy from sources such as mini hydro, or ground source energy (see Chapters 6 and 12), but most individual installations use standby heaters connected to an energy grid. One of the oldest technologies for extracting energy from sunlight and using it to heat DHW is the integrated collector storage (ICS) solar water heating, or batch system. In its simplest form, an ICS system consists of a black painted tank exposed to sunlight and with one face angled upwards. Usually the tank sits within an insulated box with a glazed sunward face. Mains water flows into and out of the tank as hot water is drawn off from the system, and there is usually an internal storage tank with a conventional water heater as...
Then I saw a movie about global warming and realized I had already begun to change my lifestyle toward living more green without too much difficulty, so why not continue I researched how to do so and found more information than I could digest. Starting small, we bought a water heater blanket, adjusted the thermostat to reflect the season, and changed all of our old lightbulbs to compact fluorescent. Immediately, we noticed a decrease in our gas and electric bills. The air conditioner got a summer off, and we installed a solar-powered attic fan to keep our suburban Salt Lake City home cooler during summertime. Our family began using organic methods in the garden instead of oil-based pesticides and fertilizers. When possible, we try to buy locally produced, fresh food. We are purchasing blocks of wind power. In the future, we are remodeling our fifty-year-old home to include hydroradiant floor heating. Another goal is to install solar panels to power our home and feed clean energy back...
Artificial neural networks have been used by the author in the field of solar energy, for modeling the heat-up response of a solar steam generating plant (Kalogirou et al., 1998), the estimation of a parabolic trough collector intercept factor (Kalogirou et al., 1996), the estimation of a parabolic trough collector local concentration ratio (Kalogirou, 1996a), the design of a solar steam generation system (Kalogirou, 1996b), the performance prediction of a thermosiphon solar water heater (Kalogirou et al., 1999a), modeling solar domestic water heating systems (Kalogirou et al., 1999b), the long-term performance prediction of forced circulation solar domestic water heating systems (Kalogirou, 2000), and the thermosiphon solar domestic water heating system's long-term performance prediction (Kalogirou and Panteliou, 2000). A review of these models, together with other applications in the field of renewable energy, is given in an article by Kalogirou (2001). In most of those models, the...
A visitor to Israel will unavoidably notice the urban landscape bursting with solar collectors and hot water storage tanks covering the roofs of buildings. Almost all residences in Israel are equipped with solar water heaters. The most common are the thermosyphonic system, a completely passive, standalone unit consisting of one or two flat plate solar collectors and an insulated storage tank. Large multistory apartment buildings often use a central system with a collector array on the roof and a storage tank in the basement, employing a pump controlled by a differential thermostat. Other arrangements are also available. In most of the country, the solar system will supply the full demand for hot water during 9-10 months per year, with an electric resistance backup employed the rest of the time. Freeze protection is never required, except in some isolated locations. The economics the installed cost of a typical single-family system comprising a 150 l storage tank and 2-3 m2 flat plate...
I Flush the garbage disposer with cold rather than hot water. The problem here is that most of the time when you turn your hot water on, you have to wait awhile for the hot water to arrive from the water heater. During this time, hot water is actually filling up the pipes between the heater and your disposer. This heat is then wasted. Even worse, in the summertime it ends up warming your home. If your air conditioner is on, it has to work harder. You lose in every way.
A vast amount of energy is wasted in heating and cooling unnecessary space due to the energy inefficient design and construction of buildings. This has arisen because traditional building regulations have paid little, if any, attention to energy efficient design. Studies have shown that energy conservation potentials of between 40 and 50 can be achieved merely by modification of building regulations.5 A variety of conservation measures, such as the installation of ceiling and wall insulation, weatherstripping, water heater blankets, low-flow shower-heads, caulking, duct wrap and solar water heaters, can have a dramatic impact on the amount of energy consumed for heating and cooling purposes.
Hot water heaters consume a lot of energy when they're on. Most of them aren't on all that much, but when they are, they gobble power up. Use a timer to turn off your hot water heater at night and during the day when you're gone. Specialty hardware stores sell special units for this purpose. The salespeople can tell you how to install them. tr When you're away from home for extended periods, turn the hot water heater off before you go. Either flip off the appropriate circuit breaker in your fuse Cqj 1 box or turn off the gas valve (in which case you'll have to relight the pilot).
The water heater in an average house has a storage tank that holds between 30 and 50 gallons of water. When cold water enters the house, from a municipal supply or a well, it is split in two parts. One goes directly to the cold taps in the plumbing fixtures, plus any toilets. The other goes to the water heater, which in turn supplies hot water to the house. A few dishwashers and clothes washers can use just cold water because they have their own heating elements, but all fixtures with hot water inlets draw from the water heater. Whether it uses a gas flame or an electric element for heating, a water heater with a tank consumes energy even when the hot water is not running. That's because the water in the tank eventually cools down, and needs to be reheated so it's ready to use. Insulation, both built-in and added on, can help keep its contents warm. Even so, this arrangement means a water heater with a tank is using energy all the time, whether or not you need it to. One other large...
The water you drain from your water heater's tank can be very hot, so be careful. Draining a quart of water directly from your water heater's tank prevents sediment buildup, which affects efficiency. If you haven't tackled this task in years, you'll be shocked at how much crud comes out.
From lower material costs to easier installations to reduced maintenance, PEX can help you save money, time, and effort. If you install a manifold at the source, with cold lines running directly from the municipal water supply and hot lines from the water heater, you can set up separate water lines for each room or even each fixture. This home run configuration brings hot water to the fixtures more quickly, saving both water and the energy used to heat it.
For example, the federal government allows a 30 percent tax credit for both hydro turbine systems and solar water-heating systems, up to a maximum of 2,000 per year. If your solar water-heater costs 6,000 to install, you get 2,000 off the price. If your hydro turbine costs 30,000, you only get 2,000 off the price. This encourages smaller investments because you save a greater percentage. The way to game this strategy is to spread your investments out over time. Install a solar water heater this year, and a hydro turbine next. And if possible, install two small systems instead of one big one.
When the water in a storage tank cools down, you need to run the tap until the cool water is flushed from the pipes. And once you use as much water as the tank had stored, you're out of luck until it heats another tankful. By contrast, a tankless water heater has a startup time of just a few seconds, so barely any water passes through the system before hot water is available. If you have chosen the right size tankless heater for your needs, it will keep heating water on demand, as long as you want. Newer models of tankless water heaters have internal thermostats and flow meters. They adjust the heat according to the volume of water being used, which provides consistent temperatures and uses only as much energy as required. When you turn off the hot water at the fixture, the tankless heater switches off automatically. Tankless water heaters can save time over the long term as well. Water heaters with tanks are only expected to work for about 10 years. Only the most expensive models are...
One way to compare the performance of water heaters is to check their energy factor (EF) ratings. Energy factor ranks energy efficiency by the average amount of hot water produced for each unit of fuel consumed. This number is made up of cycling losses (loss of heat as water circulates through the tank and pipes), recovery efficiency (how efficiently heat is transferred to the water), and standby losses Higher EF numbers translate to greater energy efficiency. When you are considering several choices, such as different fuel sources and tank options, the EF is a useful guide. It won't tell you how much a water heater will cost to operate, but it does provide a common reference. Comparing models that use natural gas or liquid propane, for example, water heaters with tanks range from EF 0.59 to 0.65, while tankless heaters get 0.69 to 0.86. In general, gas-fired tankless water heaters provide more heat faster than electric models. Because the use of natural gas or propane involves...
A solar water heater providing hot water for a family in Michigan. The system's pump is powered by the small photovoltaic panel on the left. Figure 30.2. A solar water heater providing hot water for a family in Michigan. The system's pump is powered by the small photovoltaic panel on the left.
Retracting mechanisms are available that work well enough to prevent you from hating your cover because you have to fold it up by hand every time you want to use the pool. The cheapest manual retractors cost around 300. You can install an electric retractor, but then you're starting to talk about the kind of money you spend on solar water heaters, so you may as well put in a solar water heater instead.
Hydronic systems offer some advantages over electric ones. They can be powered by a variety of energy sources, which can make a significant difference if electricity is expensive in your area. To provide the hot water needed for a hydronic system, you can use a water heater that runs on natural gas or liquid propane, a boiler that burns wood or runs on electricity, or other sources such as solar collectors, heat pumps, or geothermal energy.
A combined hydremic heating system uses warm water stored in the water heater for both domestic use and to provide heat to the units. FIGURE 3.9. A combined hydremic heating system uses warm water stored in the water heater for both domestic use and to provide heat to the units.
In order to save on utility costs and reduce your consumption of natural resources, you need a better picture of your energy use habits. Because you directly control most of the appliances and fixtures that use natural gas, you can estimate what percentages are consumed by your range, boiler or furnace, clothes dryer, water heater, and so on. But electrical consumption is harder to guess, and impossible to see.
Standards and labeling program, identified as one of the key activities for energy-efficiency improvements, is expected to ensure the availability of only energy-efficient equipment and appliances. The equipment to be initially covered under S&L program are household refrigerators, air-conditioners, water heater, electric motors, agriculture pump sets, electric lamps and fixtures, industrial fans and blowers, and air-compressors.
There is considerable potential for solar water heating to grow in the OECD, since around 20 of total residential energy consumption is for heating water. Over 90 of OECD solar water heaters are installed in the residential sector, which is expected to remain the largest consumer to 2030, although use by the commercial sector will also grow. Those heaters already provide over 7.6 Mtoe of energy for water heating, with a small proportion used for swimming pool and space heating. There is also potential for increasing use of solar water-heating systems in non-OECD countries, since the heaters are often manufactured locally and cheaply. China alone has around 60 of the world's total installed capacity and collected around 3 Mtoe of useful solar heat in 2006. Globally, solar collection used for water and space heating (not including the passive solar heating of buildings) is projected to rise to about 45 Mtoe by 2030, with widespread global distribution.
This disadvantage is removed by using compact solar heat pump systems. These incorporate an evaporator mounted outside the water storage tank with natural convection air circulation. This system needs to be installed outdoors, and if installed adjacent to the ventilation duct outlet of a building, it can also work as a waste heat recovery unit. The advantages of this system are that it has no parasitic energy requirement and, because the system is packaged, all its components are assembled in the factory and thus the system is pre-charged. The installation of this system is as simple as a conventional electric water heater because the unit requires no high-power electrical connection (Morrison, 2001).
The essential components of a solar water heater (Figure 11.15) are a set of tubes in which the water flows embedded in a black plate insulated from behind and covered with a glass plate on the side facing the Sun. A storage tank for the hot water is also required. A more efficient (though more expensive) design is to surround the black tubes with a vacuum to provide more complete insulation. Over 10 million households worldwide have solar hot water systems.49 Figure 11.15 Design of a solar water heater a solar collector connected to a storage tank through a circulating pump. Alternatively, if the storage is above the collector, the hot water will collect through gravity flow.
For locations that have a mild climate, the open loop thermosiphon solar water heater is the most widely used system. With freeze protection, thermosiphon systems can also be used in locations that experience minor freeze conditions. This can be provided by water dump valves, electric heating in the collector header, or tapered riser tubes to control ice growth in the riser so that a rigid and expanding ice plug is avoided (Xinian, et al., 1994). All these techniques have been used successfully by solar water heater manufacturers, and their suitability is proven in areas with mild freeze conditions. They are not suitable, though, in areas with hard freezing. In such cases, the only suitable design is the use of antifreeze collector loops with a heat exchanger between the collector and the tank and an antifreeze heat transfer fluid circulating in the collector and the heat exchanger. For horizontal tank configuration, the most widely adopted system is the mantle or annular heat...
New dishwashers heat their own water, which is far more efficient than drawing hot water from the water heater the way older models do. Keep this feature in mind if you're in the market for a new dishwasher. The temperature of the water from your domestic heater may affect the quality of your dishwasher's performance. If the water isn't hot enough, your machine will have a hard time doing the job. However, some detergents are rated for a lower water temperature. (For more information on water heaters, refer to the earlier section Keeping Water Heaters in Check. )
The contents of your refrigerator have to be kept cool to avoid spoiling, while the contents of your water heater do not. When you need hot water, it doesn't matter whether it was heated last week or just a minute ago. Viewed another way, the practice of keeping a tank full of hot water makes little sense. You may run the hot water for an hour a day to shower, bathe, wash hands, and wash dishes. On laundry day, you use more hot water, but still only a few hours out of the day. Yet the tank on your water heater consumes energy 24 hours a day, just to be ready for the few hours of supply you actually use. By operating only when it's needed, a tankless water heater saves all the energy that is otherwise consumed keeping a reserve supply warm. That can be as much as half of the energy a water heater uses. Tankless water heaters also make more efficient use of fuel.
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