السلام عليكم مهندسي التكيف والتبريد
انا طالبة هندسة في سنة التخرج ومحتاجة جدا الي مواضيع في
absorption refrigertion system powered by solar system
or solar air-condition system
تصميم او درجات الحرارة والضغوطات المحتاجة ....وهكذا
السلام عليكم مهندسي التكيف والتبريد
انا طالبة هندسة في سنة التخرج ومحتاجة جدا الي مواضيع في
absorption refrigertion system powered by solar system
or solar air-condition system
تصميم او درجات الحرارة والضغوطات المحتاجة ....وهكذا
تدللين المهندسة الاردنية..بأقرب وقت ان شاء الله اوفر المعلومات اللازمه
U.S. Department of Energy - Energy Efficiency and Renewable Energy
Active Solar Heating
There are two basic types of active solar heating systems based on the type of fluid—either liquid or air—that is heated in the solar energy collectors. (The collector is the device in which a fluid is heated by the sun.) Liquid-based systems heat water or an antifreeze solution in a "hydronic" collector, whereas air-based systems heat air in an "air collector."
Both of these systems collect and absorb solar radiation, then transfer the solar heat directly to the interior space or to a storage system, from which the heat is distributed. If the system cannot provide adequate space heating, an auxiliary or back-up system provides the additional heat. Liquid systems are more often used when storage is included, and are well suited for radiant heating systems, boilers with hot water radiators, and even absorption heat pumps and coolers. Both air and liquid systems can supplement forced air systems. To learn more about these two types of active solar heating, see the following sections:
Active solar heating systems are most cost-effective when they are used for most of the year, that is, in cold climates with good solar resources. They are most economical if they are displacing more expensive heating fuels, such as electricity, propane, and oil heat. Some states offer sales tax exemptions, income tax credits or deductions, and property tax exemptions or deductions for solar energy systems.
The cost of an active solar heating system will vary. Commercial systems range from $30 to $80 per square foot of collector area, installed. Usually, the larger the system, the less it costs per unit of collector area. Commercially available collectors come with warranties of 10 years or more, and should easily last decades longer. The economics of an active space heating system improve if it also heats domestic water, because an otherwise idle collector can heat water in the summer.
Heating your home with an active solar energy system can significantly reduce your fuel bills in the winter. A solar heating system will also reduce the amount of air pollution and greenhouse gases that result from your use of fossil fuels such as oil, propane, and natural gas for heating or that may be used to generate the electricity that you use.
Selecting and Sizing a Solar Heating System
Selecting the appropriate solar energy system depends on factors such as the site, design, and heating needs of your house. Local covenants may restrict your options; for example homeowner associations may not allow you to install solar collectors on certain parts of your house (although many homeowners have been successful in challenging such covenants).
The local climate, the type and efficiency of the collector(s), and the collector area determine how much heat a solar heating system can provide. It is usually most economical to design an active system to provide 40%–80% of the home's heating needs. Systems providing less than 40% of the heat needed for a home are rarely cost-effective except when using solar air heater collectors that heat one or two rooms and require no heat storage. A well-designed and insulated home that incorporates passive solar heating techniques will require a smaller and less costly heating system of any type, and may need very little supplemental heat other than solar.
Besides the fact that designing an active system to supply enough heat 100% of the time is generally not practical or cost effective, most building codes and mortgage lenders require a back-up heating system. Supplementary or back-up systems supply heat when the solar system can not meet heating requirements. They can range from a wood stove to a conventional central heating system.
Controls for Solar Heating Systems
Solar system controls.
Photo credit: Sandia National Labs.
Controls for solar heating systems are usually more complex than those of a conventional heating system, because they have to analyze more signals and control more devices (including the conventional, backup heating system). Solar controls use sensors, switches, and/or motors to operate the system. The system uses other controls to prevent freezing or extremely high temperatures in the collectors.
The heart of the control system is a differential thermostat, which measures the difference in temperature between the collectors and storage unit. When the collectors are 10°–20°F (5.6°–11°C) warmer than the storage unit, the thermostat turns on a pump or fan to circulate water or air through the collector to heat the storage medium or the house.
The operation, performance, and cost of these controls vary. Some control systems monitor the temperature in different parts of the system to help determine how it is operating. The most sophisticated systems use microprocessors to control and optimize heat transfer and delivery to storage and zones of the house.
It is possible to use a solar panel to power low voltage, direct current (DC) blowers (for air collectors) or pumps (for liquid collectors). The output of the solar panels matches available solar heat gain to the solar collector. With careful sizing, the blower or pump speed is optimized for efficient solar gain to the working fluid. During low sun conditions the blower or pump speed is slow, and during high solar gain, they run faster.
When used with a room air collector, separate controls may not be necessary. This also ensures that the system will operate in the event of utility power outage. A solar power system with battery storage can also provide power to operate a central heating system, though this is expensive for large systems.
Building Codes Covenants and Regulations for Solar Heating Systems
Before installing a solar energy system, you should investigate local building codes, zoning ordinances, and subdivision covenants, as well as any special regulations pertaining to the site. You will probably need a building permit to install a solar energy system onto an existing building.
Not every community or municipality initially welcomes residential renewable energy installations. Although this is often due to ignorance or the comparative novelty of renewable energy systems, you must comply with existing building and permit procedures to install your system.
The matter of building code and zoning compliance for a solar system installation is typically a local issue. Even if a statewide building code is in effect, it's usually enforced locally by your city, county, or parish. Common problems homeowners have encountered with building codes include the following:
Potential zoning issues include these:
- Exceeding roof load
- Unacceptable heat exchangers
- Improper wiring
- Unlawful tampering with potable water supplies.
Special area regulations—such as local community, subdivision, or homeowner's association covenants—also demand compliance. These covenants, historic district regulations, and flood-plain provisions can easily be overlooked. To find out what's needed for local compliance, contact your local jurisdiction's zoning and building enforcement divisions and any appropriate homeowner's, subdivision, neighborhood, and/or community association(s).
- Obstructing sideyards
- Erecting unlawful protrusions on roofs
- Siting the system too close to streets or lot boundaries.
Installing and Maintaining Your Solar Heating System
Periodic visual inspection may be necessary to properly maintain your solar system.
Photo credit: Robb Williamson.
How well an active solar energy system performs depends on effective siting, system design, and installation, and the quality and durability of the components. The collectors and controls now manufactured are of high quality. The biggest factor now is finding an experienced contractor who can properly design and install the system.
Once a system is in place, it has to be properly maintained to optimize its performance and avoid breakdowns. Different systems require different types of maintenance, but you should figure on 8–16 hours of maintenance annually. You should set up a calendar with a list of maintenance tasks that the component manufacturers and installer recommends.
Most solar water heaters are automatically covered under your homeowner's insurance policy. However, damage from freezing is generally not. Contact your insurance provider to find out what its policy is. Even if your provider will cover your system, it is best to inform them in writing that you own a new system.
Codes & Standards
- 2006 Uniform Solar Energy Code
Association of Plumbing and Mechanical Officials
- Solar Rating and Certification Corporation (SRCC)
Financing & Incentives
DOE Building Energy Software Tools Directory
- Find Federal Tax Credits for Energy Efficiency
- Find State and Local Incentives
Database of State Incentives for Renewables and Efficiency
- Find a Solar Pro
- PATH Tech Set #6, The Sun in the 21st Century: Passive and Active Solar Systems
Partnership for Advancing Housing Technology
- The Borrower's Guide to Financing Solar Energy Systems: A Federal Overview (PDF 501 KB). (September 1998). U.S. Department of Energy. This booklet provides an extensive overview of government-authorized special financing programs available to consumers interested in installing solar energy systems for heat and electricity.
- Starrs, T.; Nelson, L.; Zalcman, L. (1999). Bringing Solar Energy to the Planned Community (PDF 1 MB). U.S. Department of Energy. Describes neighborhood covenants as they relate to rooftop photovoltaic and solar water heating installations. Includes information on obtaining approval for your design, your legal options, and removing barriers to solar installations.
- Zehr, F.J.; Vineyard,T.A.; Barnes,R.W.; and Oneal,D.L. (November 1982). "Performance and economics of residential solar space heating." STI. See the online abstract.
- Clark, J.A. (1981). "A generalized analysis of solar space heating in the United States." Solar Engineering. See the online abstract.
- "Economic feasibility of solar water and space heating." (23 March 1979). Science (Vol. 203): p. 1214-1220. See the online abstract.
- Lof, G., ed. (1993). Active Solar Systems. Cambridge, MA: MIT Press.
- Meinel, A. and M. (1976). Applied Solar Energy: An Introduction. Addison-Wesley Publishing Co.
- Johnson, C.; Chinkes, J. (June/July 1997). "Low Cost Solar House Heating." Home Power (No. 59); pp. 44-47.
- Hunn, B., et al. (eds.) (1987). Engineering Principles and Concepts for Active Solar Systems. Solar Energy Research Institute. 312 pp.
- Meltzer, M. (1985). Passive and Active Solar Heating Technology. Columbus Circle, NY: Prentice-Hall.
- Greenwald, M.; McHugh, T. (1985). Practical Solar Energy Technology. Columbus Circle, NY: Prentice-Hall.
- Goswami, D.; Keith, F.; Kreider, J. (2000). Principles of Solar Engineering (2nd Ed.). Philadelphia, PA: Taylor and Francis.
- Jansen, T. (1985). Solar Engineering Technology. Columbus Circle, NY: Prentice-Hall.
- Duffie, J.; Beckman, W. (1992). Solar Engineering of Thermal Processes (2nd ed.). John Wiley and Sons.
- Harris, N. et al. (1985). Solar Energy Systems Design. New York: John Wiley & Sons.
- Harrell, Jr., J. (1982). Solar Heating and Cooling of Buildings. New York: Van Nostrand Reinhold.
- Paul, J. (1977). Solar Heating and Cooling, Recent Advances. Park Ridge, NJ: Noyes Data Corporation.
- Peuser, F., et al. (2002). Solar Thermal Systems: Successful Planning and Construction. James and James Science Publishers Ltd.
- Kreider, J.; Kreith, F. (1982). Solar Heating and Cooling: Active and Passive Design, 2nd Edition. New York: McGraw-Hill.
- Weiss, W., ed. (2003). Solar Heating Systems for Houses: A Design Handbook for Solar Combisystems. International Energy Agency. James & James Ltd.
- Sklar, S.; Sheinkopf, K. (1991). Consumer Guide to Solar Energy. Chicago, IL: Bonus Books, Inc.
- Anderson, B. (1991). The Fuel Savers. Lafayette, CA: Morning Sun Press.
- Anderson, B.; Riorden, M. (1987). The New Solar Home Book. Amherst, NH: Brick House.
اختي العزيزه هاي المعلومات هسه حصلت عليهه..اني تخرجت هاي السنه وعندي مصادر كثيره عنهه لكن اني ببغداد هسه والمصار بمدينتي بكركوك..ان شاء الله اجيبلج معلومات اشمل
The solar systems that will be discussed in this section are not a part of a building's structure. The function of the solar energy equipment is to convert sunlight to heat that can be used for: (a) space heating; (b) space cooling; (c) domestic hot water.
Solar systems should be employed only after extensive conservation strategies have been implemented. Solar energy systems typically have a high initial cost and extremely low operating costs. To reduce the high initial costs, reduce the size of the required system by the load that the solar system will need to provide. In space heating and cooling applications, the home should be weatherized and insulated to very high standards. In water heating applications, hot water piping should be insulated and water conserving fixtures should be used.
The goal of the solar system should not be to accomplish 100% of the home's heating, cooling, or water heating needs under all conditions. The system should be sized to reflect seasonal variations in demand and in the sun's heating characteristics. Additionally, by combining systems to perform multiple functions (i.e. space heating and water heating), the solar system investment can provide a return all year.
The City of Austin will provide a rebate under the Appliance Efficiency Program for solar domestic hot water systems if installed in an all-electric home. There are no tax incentives currently available to assist in the first costs of solar systems, but there is an exemption for solar energy devices from being appraised for property tax. There has been a dramatic reduction in the number of businesses and equipment relating to solar systems since federal tax incentives were eliminated in 1985. Only a few businesses in our area provide solar systems.
Solar installations are governed by City Ordinance 900104-J. This ordinance follows the 1988 Uniform Solar Energy Code established by IAPMO (International Association of Plumbing and Mechanical Officials). Building, plumbing, and mechanical (when the system provides space conditioning) permits are required for solar installations. There are several types of solar systems in each of the categories of space heating, water heating, and space cooling. Of the three general categories, space cooling by solar energy is the least cost effective except in passive applications, which are discussed in the Passive Solar Design section.
Active and passive solar space heating and water heating, are well-developed technologies. Active solar space cooling is marginally developed.
There are adequate suppliers on a national basis for all solar equipment except space cooling. There are few local suppliers.
Solar domestic water heaters are reasonably priced ($1000-$3500) and can show pay backs of four to seven years depending upon the fuel displaced (electric or gas). Space heating systems can vary from inexpensive wall heaters ($800) to costly large central systems ($4000+). Space cooling systems are not currently competitive. Reducing demand to keep systems small helps control costs.
Most lenders are not knowledgeable of solar systems.
There are problem areas associated with the general public perception of solar systems: solar may be considered futuristic; some may believe new technological breakthroughs are needed to make solar viable; solar systems are considered uneconomic; and, the business instability of solar system providers during the early 1980s. A primary concern for owners of a solar system is whether it can be maintained by conventional means (the owner does not have to assume extraordinary responsibilities).
City Ordinance 900104-J adopted the 1988 Uniform Solar Energy Code of IAPMO (International Association of Plumbing and Mechanical Officials). The "Solar Energy Code" is found in Chapter 13-8-500 of the Land Development Code in Article VII. The Solar Energy Code presents equipment and installation standards. Building, plumbing, and mechanical permits are required for space conditioning.
Solar energy can be captured for use in a home in several ways. This section will look at using solar energy to heat water and/or air. The hot water created by a solar system can be used for domestic hot water or space heating. Hot air solar systems are primarily used for space heating.
The fundamental requirement for a solar system is to have a sunny location where the solar collectors can be located.
Collectors can be oriented as much as 30 degrees off of south and still function well. Similarly, the slope of the collectors can vary by plus or minus 15 degrees without significantly harming the performance of the system.
- The collectors should have full sun from 9 AM to 3 PM.
The collectors should face south at approximately the same angle as our latitude (30 degrees).
2.0 Active Solar Domestic Water Heating
The active water systems that can be used to heat domestic hot water are the same as the ones that provide space heat. A space heat application will require a larger system and additional connecting hardware to a space heat distribution system.
3.0 Active Solar Space Heating
- 2.1. There are five major components in active solar water heating systems:
- Collector(s) to capture solar energy.
Circulation system to move a fluid between the collectors to a storage tank
Backup heating system
Control system to regulate the overall system operation
- 2.2 There are two basic categories of active solar water heating systems - direct or open loop systems and indirect or closed loop systems.
- 2.2.1 Direct Systems
The water that will be used as domestic hot water is circulated directly into the collectors from the storage tank (typically a hot water heater which will back up the solar heating).
There are two types of direct systems - draindown and recirculating. In both systems, a controller will activate a pump when the temperature in the collectors is higher than the temperature in the storage tank.
The draindown system includes a valve that will purge the water in the collectors when the outdoor temperature reaches 38 degrees. When the temperature is higher than 38 degrees and the collectors are hotter than the storage tank, the valve allows the system collectors to refill and the heating operation resumes.
The recirculating system will pump heated water from the storage tank through the collectors when the temperature drops to 38 degrees.
These two systems have serious drawbacks. The draindown valves can fail in a draindown system and the result can be the expensive breakage of the solar collectors. The draindown valve will typically sit unused for a very long time and then will need to work the first time without failing. The cycling of air and water in a draindown system collectors as a result of periodically draining down (thereby emptying the collectors) can cause a buildup of mineral deposits in the collectors and reduce their efficiency. The recirculating system circulates buildup from potable water heated from the storage tank through collectors during potential freeze conditions and effectively cools the water (wasting energy).
- 2.2.2 Indirect Systems
Systems that use antifreeze fluids need regular inspection (at least every 2 years) of the antifreeze solution to verify its viability. Oil or refrigerant circulating fluids are sealed into the system and will not require maintenance. A refrigerant system is generally more costly and must be handled with care to prevent leaking any refrigerant.
An indirect system that exhibits effectiveness, reliability, and low maintenance is the drainback system (see Figure 1 on next page).
The drainback system typically uses distilled water as the collector circulating fluid.
The collectors in this system will only have water in them when the pump is operating. This means that in case of power failure as well as each night, there will be no fluids in the collector that could possibly freeze or cool down and delay the startup of the system when the sun is shining.
This system is very reliable and widely used. It requires that the collectors are mounted higher than the drainback tank/heat exchanger. This may be impossible to do in a situation where the collectors must be mounted on the ground.
An indirect or direct system can be used for heating swimming pools and spas. Lower cost unglazed (no glass cover) collectors are available for this purpose.
DRAINBACK HOT WATER SYSTEM
The fluids that are circulated into the collectors are separated from the heated water that will be used in the home by a double-walled heat exchanger.
A heat exchanger is used to transfer the heat from the fluids circulating through the collectors to the water used in the home. The fluids that are used in the collectors can be water, oil, an antifreeze solution, or refrigerant.
The heat exchangers should be double-walled to prevent contamination of the household water.
The controller in these systems will activate the pumps to the collectors and heat exchanger when design temperature differences are reached.
The heat exchanger may be separate from the storage tank or built into it.
- 2.4 Guidelines summary for solar domestic water heating systems:
A well designed system will provide 50-80% of a home's hot water needs (less in winter, more in summer).
There should be 10-15 square feet of solar collector area for each person in the household.
The storage tank should hold 20-30 gallons per person.
There should be no shade on the collectors during the hours from 9:00 AM to 3:00 PM.
The collectors should face south and be tilted at a 30 degree angle (slight variations noted above will not significantly harm performance).
The collectors and storage tank should be in close proximity to the backup system and house distribution system to avoid excessive pipe losses. The pipes need to be well insulated.
Mixing valves or thermal shutoff devices should be employed to protect from excessively high temperatures.
Select systems that are tested and certified by the Solar Rating and Certification Corporation (SRCC).
The active solar space heating system can use the same operational components as the domestic water heating systems, but ties into a heating distribution system that can use heated fluids as a heat source. The distribution system includes hydronic radiator and floor coil systems, and forced air systems.
Solar collectors are also constructed that heat air. The hot air developed in such collectors can be used directly in the home during the daytime or stored in massive materials (rock or water).
4.0 Active Solar Space Cooling
- 3.1 Water Heating Collectors
- 3.1.1 The tilt of space heating collectors is generally the latitude plus 15 degrees (45 degrees in Austin).
The purpose is to align the collectors perpendicular to the sun's rays in the heating season when the optimal performance is needed.
- 3.1.2 The number of collectors used in a space heating application is based on the heat load of the house.
Average heat load / collector rated heat output = number of collectors needed.
By basing the size of the collectors on the average heat load of the home during the heating season, the system will not provide enough heat during the colder part of the heating season. Since the heat load of the house is dependent upon the extent of its energy conserving features, the greatest energy efficiency the home can have, the smaller the solar system will have to be.
- 3.1.3 The space heating system, like the domestic water heating system, must be backed up by an auxiliary heating system.
It is not practical to size a solar system to provide all of a home's heat requirement under the worst conditions. The system would become too large, too costly, and oversized for most of the time.
- 3.1.4 The storage system should be sized to approximately 1.5 gallons of storage for each square foot of collector area. The fluid that is heated and stored (typically water) can be distributed into the house heating system in the following ways:
Air distribution system - The heated water in the storage tank is pumped into a coil located in the return air duct whenever the thermostat calls for heat. The controller for the solar system will allow the pumping to occur if the temperature in the solar heated water is above a minimum amount needed to make a positive contribution to heating the home. An auxiliary heater can be used in two ways. It can add heat to the solar storage tank to maintain a minimum operating temperature in the storage tank at all times. In this case, the coil from the solar system will be located at the air handler supply plenum rather than in the return air duct. The auxiliary heater can also be a conventional furnace that will operate less often due to the warm air entering the air handler from the solar coil in the return duct.
SPACE HEATING SYSTEM
Hydronic system with radiators - The heated water is circulated in series with a boiler into radiators located in the living spaces. Modern baseboard radiators operate effectively at 140 degrees. Solar heating systems can very often reach that temperature. Using the solar system's heated water as the source of water for the boiler will reduce the boiler's energy use particularly if it senses the incoming temperature and will not operate when that temperature is above the required distribution temperature.
Hydronic system with in-slab heat - The solar heated water is pumped through distribution piping located in the floor of the home. Lower temperatures are used in this type of system (the slab is not heated above 80 degrees in most cases). The auxiliary heat can be connected in series with the solar system's heated output water or it can be connected to the solar tank to provide a minimum temperature.
In the Austin area, most homes use an air distribution system that can provide air conditioning as well as heating. The hydronic systems are much less common but are considered highly effective in terms of comfort, efficiency, and health impact (no blowing air to stir up dust). The air distribution method described above can work quite well with a conventional gas water heater as a backup. (This is discussed further in the Gas Water Heating Section.)
- 3.2 Air Collectors for Heating
Appear similar to a water collector.
Usually a black metal absorber in an insulated box with a glazed cover (glass or plastic).
Air from inside the house is drawn by a fan into a series of channels in a space behind the absorber where it is heated by the hot absorber plate. The heated air then enters the home directly or enters a storage medium (such as rocks) so the heat will be available during the night.
A simple controller is used to turn on the fan(s) in this type of system. The controller uses sensors in the collector to activate the system when it is hotter in the collector than in the house interior or storage medium.
Air collectors can be mounted vertically on the south wall of a building if used for space heating only. In that location, properly designed overhang will prevent them from heating up in the summer.
For a year-round application of air heating collectors, it is necessary to use an air-to-water heat exchanger. This is not a very efficient system for heating water compared to fluid circulating collectors, since heat (and thus efficiency) is lost at each transfer point.
Air collectors are more practical in climates with longer and colder winters than in Austin. The investment in storage systems for air collectors is substantial in time, money, and materials. The use of air collectors to put heat into the house directly can be readily achieved with properly oriented windows in our area. Daytime temperatures in the winter can be relatively high; the additional hot air from an air collector can overheat a home that does not have extra thermal mass to absorb the heat.
Solar space cooling is quite costly to implement. If the solar system is used for space cooling only, installed costs can run $4,000-$8,000 per ton. It is best to use a solar system that serves more than just the cooling needs of a house to maximize the return on investment and not leave the system idle when cooling is not required. Significant space heating and/or water heating can be accomplished with the same equipment used for the solar cooling system.
SCHEMATIC OF SOLAR ABSORPTION COOLING SYSTEM
T = system flow sequence
5.0 Passive Solar Water Heating
- 4.1 The technologies that are being developed for gas cooling systems are the same ones being developed for active solar space cooling systems. Desiccant cooling systems and advanced absorption systems are the primary technologies that are used. High temperature liquid collectors are typically used in these systems.
- 4.1.1 Desiccant system
A moisture absorbing material (desiccant) is located in the air stream going into the living space. As the air passes through the desiccant, which is usually located on a wheel that slowly rotates into the air stream, moisture is removed from the air, dropping the humidity level in the air stream to the point that an evaporative cooler can then cool the air. The desiccant is dried by the heat generated by the solar collectors as it rotates out of the air stream.
- 4.1.2 Absorption air conditioning
Heat from solar collectors separates a low boiling refrigerant in a generator which receives the pressurized refrigerant from an absorber. Solar heat can also be used in the evaporation stage of the cycle.
A passive solar water heating system uses natural convection or household water pressure to circulate water through a solar collector to a storage tank or to the point of use. Active systems employ pumps and controllers to regulate and circulate water. Although passive system are generally less efficient than active systems, the passive approach is simple and economical.
Passive water heating systems must follow the same parameters for installations as active systems - south facing unshaded location with the collector tilted at the angle of our latitude. Since the storage tank and collector are combined or in very close proximity, roof structural capacities must accommodate the extra weight of a passive system which can be 300 pounds or more.
- 5.1 There are two types of passive water heaters : batch and thermosyphon
- 5.1.1 Batch System
The batch system is the simplest of all solar water heating systems.
SCHEMATIC FOR GROUND-MOUNT BATCH DOMESTIC WATER SYSTEM
It consists of one or more metal water tanks painted with a heat absorbing black coating and placed in an insulating box or container with a glass or plastic cover that admits sunlight to strike the tank directly. The batch system's storage tank is the collector as well. These systems will use the existing house pressure to move water through the system. Each time a hot water tap is opened, heated water from the batch system tank is removed and replaced by incoming cold water.
The piping that connects to and from the batch heater needs to be highly insulated. On a cold night when no one is drawing hot water, the water in the pipes is standing still and vulnerable to freezing. In many applications, insulated polybutylene piping is used because the pipe can expand if frozen. The water in the batch heater itself will not freeze because there is adequate mass to keep it from freezing.
Since the tank that is storing the heated water is sitting outside, there will be heat loss from the tank during the night. This can be minimized by an insulating cover placed on the heater in the evening.
The most effective use of a batch water heater is to use hot water predominantly in the afternoon and evenings when the temperature in the tank will be highest. Manufactured batch heaters have a "selective surface" coating on the tanks that will absorb heat most readily yet permits very little heat loss. This feature is very valuable in these type of systems as it helps insulate the tank.
- 5.1.2 Thermosyphon Systems
The thermosyphon system uses a flat plate collector and a separate storage tank that must be located higher than the collector.
The collector is similar to those used in active systems.
The storage tank, located above the collector receives heated water coming from the top of the collector into the top of the storage tank. Colder water from the bottom of the storage tank will be drawn into the lower entry of the solar collector to replace the heated water that was thermosyphoned upward. The storage tank may or may not use a heat exchanger. The thermosyphon system is more costly and complex than the batch system. In our area, it is best to use an indirect system (one that employs a heat exchanger). In that case, antifreeze can be used in the system eliminating freeze ups.
- 5.1.3 Sizing
The sizing of a batch system and thermosyphon system are both based on a usage figure of 20 gallons of hot water per person per day. For example, if the storage tank in these systems is 40 gallons, that would equal the requirement for two people. The collector area in the thermosyphon system should equal approximately 20 square feet per person.
The system is not sized for 100% of the energy requirement. A backup source is needed.
السلام عليكم..اختي المهندسة الاردنية جبت بعض المعلومات اتمنى تستفادين منهه..انتي تحتاجيهه بمادة الطاقة المتجده اكيد..احنه درسناهه بالمرحلة الرابعة وهي مادة حلوه ومهضومة..
تمنياتي لكِ بالنجاح والتخرج.
اشكرك جزيل الشكر في ميزان حسناتك ان شاء الله
عنجد انا في قمة الحاجة لهالمعلومات
التكيف بهذه الطريقة رح يكون موضوع مشروع التخرج ان شاء الله
اذا عندك معلومات تصميمية يا ريت تبعتلي اياهم وشكرا مرة اخرى
حلوة يا بلدي
لاتشكريني اختي العزيزة هذا واجبي..ان شاء الله اجيب كل المعلومات التصميمية
اقدم هذا الملف وهو يحتوي على بعض من تجارب الاخرين في هذا المجال , ولكن للاسف لايحتوي على معلومات تصميمية , تحياتي
اختى الفاضلة اذا وجتى معلومات
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