TECHNICAL INSTRUCTIONS SOLAR WATER HEATER

Transcription

1 TI 03/2009 TECHNICAL INSTRUCTIONS ON SOLAR WATER HEATER BY DTE OF WORKS ENGINEER-IN-CHIEF S BRANCH INTEGRATED HQ OF MOD (ARMY) 1

2 FOREWORD With the fast depletion of conventional energy sources, thrust is gradually shifting to use of new and renewable energy sources. The global warming and green house effects caused due to burning of fossil fuels is recognized as major threat to mankind. The use of solar energy is the need of the day, which should be harnessed to the extent possible to conserve the limited stock of hydrocarbons. It is, therefore, a major concern and has appropriately drawn our attention. TI 03/2009 has been formulated to provide information with regards to harnessing the potential of solar energy for water heating application, its advantages and various technical parameters required for its implementation. It also covers the various aspects during installation and subsequent maintenance. This TI will help the executives to understand and maintain the system optimally. Publication of this TI would assist in achieving the vision of the MES i.e. to develop the MES into a competent, efficient, responsive, cost effective and technologically advanced organization in service to the Defence Forces and the National construction Effort. Another initiative in our Quest For Excellence. I am sanguine that this TI would guide all executives and staff in achieving enhanced standards. I expect its contents to be followed explicitly, to serve our ongoing thrust towards increasing use of non-conventional and renewable energy sources. New Delhi Mar 09 (GUTAM DUTT) Lt Gen E-in-C 2

3 PREFACE Energy is precious and there is a need to harness solar energy available in abundance in our country. Solar water heaters can provide a viable means to facilitate easy, safe and economical utilisation of solar energy for convenience of troops and families of armed force personnel spread in difficult and unapproachable areas of the country. This technical instruction (TI) not only introduces the concept but also gives in-depth details of technology for effective and economical tapping of vast natural resource. Solar water heaters can provide a cost effective system which integrates convenience with economy and independence of use irrespective of location. These heaters are also a means of energy storage conceding advantages of conservation of energy. Being a renewable source of energy, it helps in protecting environment and reduces global warming effects. Various designs of solar water heaters have been introduced, explained and compared in the TI for convenience of selection of appropriate type and layout most suitable for specific requirement. The TI also elaborates practical instructions essential for installation and maintenance and inspection of solar water heaters. Troubleshooting have been well defined and covered in details so that the TI can work as a handbook for practicing engineer in field. Convoluted data compilation for sizing and pointing of solar heaters has been presented in tabular form for ease of designers located in intricate parts of the country. New Delhi Mar 09 Brajesh Kumar Maj Gen DG (Works) 3

4 CONTENTS SOLAR WATER HEATER TOPIC PAGE NOs 1. INTRODUCTION 4 2. WHY SOLAR ENERGY ONLY 4 3. APPLICATIONS 5 4. HOW THEY WORK 5 5. ECONOMICS, ENERGY AND SYSTEM COSTS TYPES 6 7. ACTIVE SYSTEMS 6 8. PASSIVE SYSTEMS 7 9. THERMAL COLLECTOR SITING SELECTION CRITERIA RECOMMENDED CAPACITY OF SOLAR HEATERS SOLAR WATER HEATING ENERGY EFFICIENCY INSTALLATION AND MAINTENANCE TROUBLESHOOTING PERIODIC INSPECTION GLOSSARY OF TERMS INDIAN STANDARDS PARAMETERS FOR SIZING AND POINTING OF SOLAR PANELS 4

5 1. INTRODUCTION The system which turns cold water into hot water with the help of solar insolation is called Solar Water Heating System (SWHS). Solar heating systems are generally composed of solar thermal collectors, a fluid system to move the heat from the collector to its point of usage. The system may use electricity for pumping the fluid, and have a reservoir or tank for heat storage and subsequent use. The systems may be used to heat water for a wide variety of uses, including home, business and industrial uses. In many climates, a solar heating system can provide up to 85% of domestic hot water required. Residential solar thermal installations can be subdivided into two kinds of systems; compact and pumped systems. Both typically include an auxiliary energy source (electric heating element or connection to a gas or fuel oil central heating system) that is activated when the water in the tank falls below a minimum temperature setting such as 50 C. Hence, hot water is always available. The rise in temperature depends on solar radiation, weather conditions and no. of solar collectors. 2. WHY SOLAR ENERGY Available Free of Cost. Available abundantly in India. Earth receives only 2% of total radiation emitted by the Sun. Solar Energy available on Earth is 10, 000 times more than yearly requirement. Pollution Free. Maintenance free. Savings in : o o o Natural Resources Electricity Bills Foreign Exchange 5

6 3. APPLICATIONS a) Married Accn b) OTM Accn, Cook Houses, Guest rooms, MES IB etc. c) Hospitals, MI Rooms, Workshops etc Designs suitable for hot climates can be much simpler and cheaper, and can be considered an appropriate technology for these places. The global solar thermal market is dominated by China, Europe, Japan and India. 4. HOW THEY WORK Solar water heating systems include storage tanks and solar collectors. There are two types of solar water heating systems: active, which have circulating pumps and controls, and passive, which don't have circulating pumps and controls. Most solar water heaters require a well-insulated storage tank. Solar storage tanks have an additional outlet and inlet connected to and from the collector. In two-tank systems, the solar water heater preheats water before it enters the conventional water heater. In one-tank systems, the back-up heater is combined with the solar storage in one tank. In order to heat water using solar energy, a collector is fastened to the roof of a building, or on a wall facing the sun. In some cases, the collector may be free-standing. The working fluid is either pumped (active system) or driven by natural convection (passive system) through it. The collector could be made of a simple glass topped insulated box with a flat solar absorber made of sheet metal attached to copper pipes and painted black, or a set of metal tubes surrounded by an evacuated (near vacuum) glass cylinder. In some cases, before the solar energy is absorbed, a parabolic mirror is used to concentrate sunlight on the tube. A simple water heating system would pump cold water out to a collector to be heated, the heated water flows back to a collection tank. This type of collector can provide enough hot water for an entire family. 5. ECONOMICS, ENERGY AND SYSTEM COSTS In sunny, warm locations, where freeze protection is not necessary, a batch type solar hot water heater can be extremely cost effective. In higher altitudes, there are often additional design requirements for cold weather, which add to system complexity. This has the effect of increasing the initial cost (but not the life-cycle cost) of a solar hot water system, to a level much higher than a comparable hot water heater of the conventional type. When calculating the total cost to own and operate, a proper analysis will consider that solar energy is free, thus greatly reducing the operating costs, whereas other energy sources, such as gas and electricity, can be quite expensive over 6

7 time. Thus, when the initial costs of a solar system are properly financed and compared with energy costs, then in many cases the total monthly cost of solar heat can be less than other more conventional types of water heaters. In addition, Govt sponsered incentives can be significant Solar water heaters lower the cost of electric bills. A typical consumer can save about 30%-50% on electric bill, while lessening the use of oil and the impact on the environment. solar heater will pay back its investment in 2-3 years, through recurring energy savings. Besides with the government push towards tapping solar power, easy loans from nationalized banks at nominal interest rates are also available. 6. TYPES Solar hot water systems can be classified in different ways: The type of collector used The location of the collector - roof mount, ground mount, wall mount The location of the storage tank in relation to the collector The requirement for a pump - active vs. passive The method of heat transfer - open-loop or closed-loop 7. ACTIVE SYSTEMS (Pumped systems) There are two types of active solar water heating systems: DIRECT CIRCULATION SYSTEMS Pumps circulate household water through the collectors and into the home. They work well in climates where it rarely freezes. INDIRECT CIRCULATION SYSTEMS Pumps circulate a non-freezing, heat-transfer fluid through the collectors and a heat exchanger. This heats the water that then flows into the home. They are popular in climates prone to freezing temperatures How the solar water heating system is pumped and controlled determines whether it is a zero carbon or a low carbon system. Low carbon systems principally use electricity to circulate the fluid through the collector. The use of electricity typically reduces the carbon savings of a system by 10% to 20%. New zero carbon solar water heating systems are powered by solar electric (photovoltaic or PV) pumps. These typically use a 5-20W PV panel which faces in the same direction as the main solar heating panel and a small, low flow diaphragm pump to pump the water. 7

8 8. PASSIVE SYSTEMS (Compact systems) Passive solar water heating systems are typically less expensive than active systems, but they're usually not as efficient. However, passive systems can be more reliable and may last longer. There are two basic types of passive systems: INTEGRAL COLLECTOR-STORAGE PASSIVE SYSTEMS These work best in areas where temperatures rarely fall below freezing. They also work well in households with significant daytime and evening hot-water needs. THERMOSYPHON SYSTEMS Water flows through the system when warm water rises as cooler water sinks. The collector must be installed below the storage tank so that warm water will rise into the tank. These systems are reliable, but require careful attention to the roof design because of the heavy storage tank. They are usually more expensive than integral collector-storage passive systems. A compact system can save up to 4.5 tonnes annually of greenhouse gas emissions. In order to achieve the aims of the Kyoto Protocol, several countries are offering subsidies to the end user. Some systems can work for up to 25 years with minimum maintenance. These kinds of systems can be redeemed in six years, and achieve a positive balance of energy (energy used to build them minus energy they save in 1.5 years). 9. THERMAL COLLECTOR There are three main kinds of solar thermal collectors in common use. In order of increasing cost they are: Formed Plastic Collectors, Flat Collectors, and Evacuated Tube Collectors. The efficiency of the system is directly related to heat losses from the collector surface. Heat losses are predominantly governed by the thermal gradient between the temperature of the collector surface and the ambient temperature. Efficiency decreases when either the ambient temperature falls or as the collector temperature increases. This decrease in efficiency can be mitigated by increasing the insulation of the unit by sealing the unit in glass e.g. flat collectors or providing a vacuum seal e.g. evacuated tube collector. The choice of collector is determined by the heating requirements and environmental conditions in which it is employed. FORMED PLASTIC COLLECTOR Formed plastic collectors (such as polypropylene, EPDM or PET plastics) consist of tubes or formed panels through which water is circulated and heated by the sun's radiation. These are often used for extending the swimming season in swimming pools. This panel is not suitable for year-round uses like providing hot water for home use, primarily due to its lack of insulation which reduces its effectiveness greatly when the ambient air temperature is lower than the temperature of the fluid being heated. 8

9 FLAT PLATE COLLECTOR A flat plate collector consists of a thin absorber sheet (of thermally stable polymers, aluminium, steel or copper, to which a black or selective coating is applied) backed by a grid or coil of fluid tubing and placed in an insulated casing with a glass or polycarbonate cover. Fluid is circulated, using either mains or solar electricity, through the tubing to remove the heat from the absorber and to transport it to an insulated water tank, sometimes directly or otherwise to a heat exchanger or to some other device for using the heated fluid. Some fabricants have a completely flooded absorber consisting of 2 sheets of metal stamped to produce a circulation zone. Because the heat exchange area is greater they may be marginally more efficient than traditional absorbers. Most flat plate collectors have a life expectancy of over 25 years. EVACUATED TUBE COLLECTOR Vacuum tube collectors technology is superior to other prevalent systems in performance, reliability & ease of installation. Breakthrough technology that taps the unlimited power of the sun to give you enormous energy savings year after year. solar water heater will continue to function even on cloudy days due to heat absorption from diffused solar insolation. Efficiency would be affected, however, on rainy days.hot water produced by the solar system during the day is stored in an insulated storage tank. The insulation of the tank is such that the water remains hot without significant drop in temperature for around 24 hrs. Thus water heated during the previous day is available for use the next morning FEATURES a. Heating from diffused rays of solar radiation which comprises of approximately 36% of all solar radiation. b. Greater absorption area per day c. Greater absorption time per day 9

10 d. Minimum heat loss from the system due to the vacuum tubes & PUF insulated storage tank e. Better performance in winter & on cloudy days. Up to 10 o C higher temperature f. Maintenance free, easy to clean g. Compact size - low height & lesser space required for installation. WORKING The Vacuum Tube Collector solar water heater is made up of rows of parallel, transparent glass tubes. Each tube consists of a glass outer tube and an inner tube, or absorber, covered with a selective coating that absorbs solar energy well but inhibits radioactive heat loss. The air is withdrawn ("evacuated") from the space between the tubes to form a vacuum, which eliminates conductive and convective heat loss. The Vacuum tube collector absorbs the heat from the solar radiation & heats up the water stored in the system through the Thermosiphonic Effect. Evacuated tube collectors heat to higher temperatures, with some models providing considerably more solar yield per square metre than flat panels. However, they are more expensive and fragile than flat panels. Evacuated heat tubes perform better than flat plate collectors in cold climates because they only rely on the light they receive and not the outside temperature. The high stagnation temperatures can cause antifreeze to break down, so careful consideration must be 10

11 used if selecting this type of system in temperate climates. In extremely hot climates, flat-plate collectors will generally be a more cost-effective solution than evacuated tubes. When employed in arrays of 20 to 30 or more, the efficient but costly evacuated tube collectors have net benefit in winter and also give real advantage in the summer months. They are well suited to extremely cold ambient temperatures and work well in situations of consistently low-light.. Properly designed evacuated tubes have a life expectancy of over 25 years which greatly adds to their value. COMPARISON OF VACUUM TUBE & FLAT PLATE COLLECTOR Vacuum tube collector 1. Heat absorptions from the infrared rays of solar radiation instead of the visible light rays, so during winter and cloudy days, the system absorbs infrared rays as usual. 2. Heat absorbing surface is always perpendicular to sunlight because of spherical collectors Flat Plate collector Heat absorption occurs from the visible light rays, On cloudy days performance will be affected significantly. Heat absorption surface will be perpendicular to sunlight only for a short time. 3. Heating continues till late evening It falls down after 2 p.m 4. It gives 10 o C higher temperature of hot water in winter & Cloudy days. 5. The vacuum inside the collector tubes vastly reduces overnight heat loss 6. Salt or scale formation when using hard water will be reduced 7. Scale deposits slide off the smooth glass walls to accumulate at the bottom from where they can be easily removed. It is not possible in FPC as heating efficiency falls significantly on cloudy and winter days. Heat loss will be more at night from collector panels. Scale formation will be more and may choke the narrow pipes within the collector. Once the scale deposits are formed it stops the flow of water; the removal of scale is also some what difficult. 8. Installation of the system is very easy Installation of the system is not easy as VTC 9. Area required for installation will be very less 10. Incase of damage to the collector tubes, individual tube can be replaced. It require more area compared to VTC But here entire flat plate has to be replaced and it involves high cost for replacement. 11

12 10. SITING SOLAR WATER HEATING SYSTEM S COLLECTOR Both the orientation and tilt of the collector affect solar water heating system's performance. Consider both factors while evaluating system. COLLECTOR ORIENTATION Solar hot water collectors should be oriented geographically to maximize the amount of daily and seasonal solar energy that they receive. In general, the optimum orientation for a solar collector in the northern hemisphere is True South. However, recent studies have shown that, depending on location and collector tilt, collector can face up to 90º east or west of true south without significantly decreasing its performance. factors such as roof orientation, local landscape features that shade the collector daily or seasonally, and local weather conditions (foggy mornings or cloudy afternoons), may affect collector's optimal orientation. COLLECTOR TILT Today, most solar water heating collectors are mounted flat on the roof. This is more aesthetically pleasing than rack-mounted collectors, which stick up from the roof at odd angles. The optimal tilt angle for collector is an angle equal to latitude of that place(s). 11. SELECTION CRITERIA Before you purchase and install a solar water heating system, you want to do the following: Consider the economics of a solar water heating system Evaluate your site's solar resource Determine the correct system size Determine the system's energy efficiency Estimate and compare system costs Investigate local codes, covenants, and regulations. 12

13 12. RECOMMENDED SCALES OF SOLAR WATER HEATERS IN MES Sl.No. Description Solar Water Heater with Electric Backup 1. Officers & Nursing officers, single living accommodation & Guest rooms in officers mess 2. Married & separated family accommodation For moderate climates (Plains of rest of country and coastal climates 100 Ltrs/day/group of 8 officers or a part there of 100 Ltrs/day/family (System should be independent preferably For extreme climates (Plains of Northern and Western India) cold climates (Hilly regions of South/Northern/North West and Eastern India 100 ltrs/days/group of 4 officers or a part there of 200 ltrs/day/family (system should be independent preferable) a) Officers/Nursing Officers b) JCO s/ncos/or c) Defence civilian officers 3. Officers,Nursing Officers,JCOs Messes & Officers Institutes 100 ltrs/day/family (system should be independent preferably) 100 ltrs/day/family (system should be independent preferably) 200 ltrs/day/mess 200 ltrs/day/family (system should be independent preferably 200 ltrs/day/family(system should be independent preferably) 400 ltrs/day/mess 13

14 4. Or Cook houses & institutions 300 ltrs/day/cook house 500ltrs/day/cook house 5. Inspection Bunglows: 100 Ltrs per day per 2 suits 200 Ltrs/day/per 2 suits 6. JCOs or single living accommodation 7. Veterinary Hospital and units sick lines 200 Ltrs/day/100 mess barrack Central Solar Water eating ltrs per days per 5 Jawans in cold areas wherever approved by GOC-in-C As requried 13. SOLAR WATER HEATING ENERGY EFFICIENCY For a solar water heating system, use the solar energy factor (SEF) and solar fraction (SF) to determine its energy efficiency. The solar energy factor is defined as the energy delivered by the system divided by the electrical or gas energy put into the system. The higher the number, the more energy efficient. Solar energy factors range from 1.0 to 11. Systems with solar energy factors of 2 or 3 are the most common. Another solar water heater performance metric is the solar fraction. The solar fraction is the portion of the total conventional hot water heating load (delivered energy and tank standby losses). The higher the solar fraction, the greater the solar contribution to water heating, which reduces the energy required by the backup water heater. The solar fraction varies from 0 to 1.0. Typical solar factors are

15 14. INSTALLIATION AND MAINTENANCE The proper installation of solar water heaters depends on many factors. These factors include solar resource, climate, local building code requirements, and safety issues. After installation, properly maintaining your system will keep it running smoothly. Passive systems don't require much maintenance. Plumbing and other conventional water heating components require the same maintenance as conventional systems. Glazing may need to be cleaned in dry climates where rainwater doesn't provide a natural rinse. Regular maintenance on simple systems can be as infrequent as every 3 5 years, preferably by a Authorized dealer/manufacturer. INSTALATION INSTRUCTIONS The position you will choose for the installation of the solar water heater, should not be shaded by any obstacles (trees, buildings etc) all around the year. The installation should be done according to the electric and plumbing regulations applicable. In regions subject to heavy snowfall, it is very important to ensure, that too much snow does not accumulate behind the storage tank, and to check if the supports of the standard equipment are good enough to withstand the weight of the expected snow. The same attention must be paid, for regions with high velocity winds and storms. In these cases, the storage tank must be fixed firmly to the roof and must be tightened with the additional metal straps. It is absolutely necessary to use the typhoon set. The tubes of the solar water heater as well as the cold/hot water piping must be very well insulated. For installation on a flat surface, check the density, hardness and strength of the concrete. For installation on a sloping roof, additional rafters must be installed under the tiles, so that the distance between the rafters does not exceed 50cm, and their strength mush be good enough for the safe installation of the appliance. Sacrificial anode be provided in storage tank to protect tank from galvanic corrosion. Storage tank shall be made of stainless steel grade 304. CPVC pipes should be used instead of GI pipes for hot water for reliability. Electrical back up should be provided to mitigate inefficient functioning on cloudy days. 15

16 INSTRUCTIONS AFTER THE INSTALLATION The solar water heater reaches the optimum performance two days after the installation. During these two days, it is recommended to avoid the hot water consumption, even if there is sunshine. Check every year the level of the fluid in the closed circuit In regions with too much dust, clean the glass of the collector with water, every two months in order to remove the dust from the glass, unless there is enough rain. In case of a glass damage, replace the glass immediately to avoid further damage of the collector. For all water heaters, the main principles and codes require that the function of the valves is checked once a year During a long absence (such as summer holidays), it is recommended to cover the collector(s) with an opaque cover. Only potable/clean soft water having total hardness less than 50 PPM (parts per million) should be used in the SWHS. The most efficient operating times for the unit are between Morning (Sunrise) till Evening (Sunset). But this will depend on season of year & density of cloud cover, if any. In days of dense cloud cover excessive water usage should be avoided. Large withdrawal of hot water during daytime will result into poor hot water supply next day morning. Adequate length of cold water inlet pipeline, entire length of outlet hot water pipeline and portion of the pipeline between the collector and tank must be insulated to prevent loss of heat from the system to the atmosphere. Overhead cold water tank be placed 4-6 above the collector and kept always full to avoid air trapping in the system. By using rock wool pads having density of 48 Kg/M 3 with thermal conductivity of W/deg K. Thickness of insulation shall be kept 25 mm to 40 mm for pipe lines and covered with 22 SWG aluminium sheet cladding. Cold water tank should be at least 1.5 to 2 times the solar tank capacity. 16

17 15. TROUBLESHOOTING Problem Cause Remedy Not getting hot a) The Solar Product is located in a) Relocate in unshaded area water? shaded. during the day. b) Wrong connection of cold b) Connect according to water & hot water pipes to instructions. storage tank. Water is not coming? Hot water flow not smooth? Getting Luke warm water? Water is boiling in the collector? Electrical backup working not c) Air is trapped in the collector or tank. If required, drain the system & fill it again. c) Open the collector's upper plug & remove the air. d) Non Return valve not working. d) Remove & clean Non return valve spring. e) Filter choked e) Remove the cap & clean the screen of the filter. a) Pipes of hot or cold water in the storage tank are choked by sediment. a) Clean the pipes & descale sedimentation. b) Cold water tank is empty. b) Fill the overhead cold water tank. a) Air vent for Hot/Cold water a) Provide suitable ARV/Air vent tank is not provided. for the both the tanks. a) Cloudy day. a) Use electrical backup, if provided. b) Collectors not cleaned. b) Remove dust accumulated on the collector. c) Mixing of cold & hot water. c) Check mixers & install the non return valve, if required. d) Hot water pipeline not insulated properly. e) Scale formation in the collector. d) Insulate the pipeline with suitable insulation. e) Descale the collector & use soft water to avoid this problem in future. a) Not in use for a long time. a) Cover the collector with a shade. b) Failure of Thermostat. b) Change the Thermostat. a) Wrong wiring connections. a) Connect according to the wiring diagram. b) Loose wiring connections. b) Locate, clean carefully & reconnect tightly. c) Lightening. c) Inspect / replace fuse, heater element & thermostat. d) Short circuit. d) Inspect / replace fuse, heater element & thermostat. e) Heater Thermostat failure. e) Replace with a new one. 17

18 16. PERIODIC INSPECTION Some suggested inspections of solar system components:- Collector shading Visually check for shading of the collectors during the day on an annual basis. Shading can greatly affect the performance of solar collectors. Vegetation growth over time or new construction may produce shading that wasn't there when the collectors were installed. Collector soiling Dusty or soiled collectors will perform poorly. Periodic cleaning may be necessary in dry, dusty climates. Collector glazing and seals Look for cracks in the collector glazing, and check to see if seals are in good condition. Plastic glazing, if excessively yellowed, may need to be replaced. Plumbing, ductwork, and wiring connections Look for fluid leaks at pipe connections. Check duct connections and seals. Ducts should be sealed with a mastic compound. All wiring connections should be tight. Piping, duct, and wiring insulation Look for damage or degradation of insulation covering pipes, ducts, and wiring. Roof penetrations Flashing and sealant around roof penetrations should be in good condition. Support structures Check all nuts and bolts attaching the collectors to any support structures for tightness. Pressure relief valve (on liquid solar heating collectors) Make sure the valve is not stuck in open or closed position. 18

19 Dampers (in solar air heating systems) If possible, make sure the dampers open and close properly. Pumps or blowers Verify that distribution pumps or blowers (fans) are operating. Listen to see if they come on when the sun is shining on the collectors after mid-morning. If not, then either the controller has malfunctioned or the pump or blower has. Heat transfer fluids Antifreeze solutions in liquid (hydronic) solar heating collectors need to be replaced periodically. It's a task best left to a qualified technician. If water with a high mineral content (i.e., hard water) is circulated in the collectors, mineral buildup in the piping may need to be removed by adding a de-scaling or mild acidic solution to the water every few years. Storage systems Check storage tanks, etc., for cracks, leaks, rust, or other signs of corrosion. 17. GLOSSARY OF TERMS Air mass (sometimes called air mass ratio) Equal to the cosine of the zenith angle-that angle from directly overhead to a line intersecting the sun. The air mass is an indication of the length of the path solar radiation travels through the atmosphere. An air mass of 1.0 means the sun is directly overhead and the radiation travels through one atmosphere (thickness). Angle of Incidence The angle that a ray of sun makes with a line perpendicular to the surface. Annual Solar Savings The annual solar savings of a solar building is the energy savings attributable to a solar feature relative to the energy requirements of a non-solar building. Azimuth Angle The angle between true south and the point on the horizon directly below the sun. Combined Collector A photovoltaic device or module that provides useful heat energy in addition to electricity. Days of Storage The number of consecutive days the stand-alone system will meet a defined load without solar energy input. This term is related to system availability. 19

20 Diffused Insolation Sunlight received indirectly as a result of scattering due to clouds, fog, haze, dust, or other obstructions in the atmosphere. Opposite of direct insolation. Diffused Radiation Radiation received from the sun after reflection and scattering by the atmosphere and ground. Direct Insolation Sunlight falling directly upon a collector. Opposite of diffuse insolation Langley (L) Unit of solar irradiance. One gram calorie per square centimeter. 1 L = kwh/m2. Orientation Placement with respect to the cardinal directions, N, S, E, W; azimuth is the measure of orientation from north. Packing Factor The ratio of array area to actual land area or Pyranometer An instrument used for measuring global solar irradiance. Pyrheliometer An instrument used for measuring direct beam solar irradiance. Uses an aperture of 5.7 to transcribe the solar disc. Solar Constant The average amount of solar radiation that reaches the earth's upper atmosphere on a surface perpendicular to the sun's rays; equal to 1353 Watts per square meter or 492 Btu per square foot. Solar Cooling The use of solar thermal energy or solar electricity to power a cooling appliance. Photovoltaic systems can power evaporative coolers ("swamp" coolers), heat-pumps, and air conditioners. Solar Insolation The amount of solar radiation available at a location. Solar Resource The amount of solar insolation a site receives, usually measured in kwh/m2/day, which is equivalent to the number of peak sun hours. Tilt Angle The angle at which plate collector is set to face the sun relative to a horizontal position. The tilt angle can be set or adjusted to maximize seasonal or annual energy collection. Zenith Angle the angle between the direction of interest (of the sun, for example) and the zenith (directly overhead). 20

21 18. INDIAN STANDARDS Document Number IS : 1986 IS : Part 2 : 1993 IS : Part 3 : 1998 IS : 1989 IS : Part 1 : 2003 IS : Part 2 : 2003 IS : Part 3 : 2003 IS : Part 5 : 2003 IS : 1990 IS : Part 1 : 1991 IS : Part 2 : 1991 IS : Part 3 : 1991 IS : Part 4 : 1991 Standard Title Recommendations for calculation of solar radiation on buildings Photovoltaic devices: Part 2 Requirement for reference solar cells Photovoltaic Devices"- Part 3 : Measurement Principles for Terrestrial Photovoltaic Solar Devices with Reference Spectral Irradiance Data Solar photovoltaic energy systems-terminology Solar Flat Plate Collector - Specification - Part 1 : Requirements Solar Flat Plate Collector - Specification - Part 2 : Components Solar Flat Plate Collector - Specification - Part 3 : Measuring Instruments Solar Flat Plate Collector - Specification - Part 5 : Test Methods Code of practice for solar water heating systems Solar heating - Domestic water heating system: Part 1 Performance rating procedure using indoor test methods Solar heating - Domestic water heating systems: Part 2 Procedure for system performance characterization and yearly performance predication Solar heating - Domestic water heating systems: Part 3 Procedure for system component characterization and predication for yearly performance using component performance data Solar heating - Domestic water heating system: Part 4 Determination of durability and reliability 21

22 Sr Location No 19. PARAMETERS FOR SIZING AND POINTING OF SOLAR PANELS - (Monthly Averaged Insolation (kwh/m 2 /day) in major mil stations/ cantonments in India) Latitude / Longitude 22-year Average Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual Average 1 Abohar / Agra / Ahmadabad 19.1 / Ahmadnagar / Allahabad / Alwar / Ambala 1.383/ Amritsar / Amroha 28.95/ Bangalore / Bareilly / Bathinda / Belgaum 50.25/ Bharatpur / Bhuj 23.25/ Bikaner / Car Nicobar 9.167/ Chandigarh / Chennai 13.1 / Coimbatore / Dalhousie / Dehra Dun 30.35/ Delhi / Dharamshala 32.2/ Fatehgarh / Firozpur 30.9/ Gandhinagar 23.2/

23 28 Ganganagar / Gangtok 27.35/ Goa / Gorakhpur / Gurdaspur / Gurgaon / Guwahati / Gwalior / Hisar / Hyderabad / Itarsi / Jabalpur / Jaipur / Jaiselmer 26.9/ Jalandhar / Jammu 32.75/ Jhansi 25.45/ Jodhpur / Jorhat / Kalimpang / Kanpur / Kapurthala / Kochi 8.983/ Kohima 25.7/ Kolkata / LadakhRange / Leh / Lucknow / Ludhiana / Mangalore / Mathura 27.5/ Meerut 29/ Mumbai / Nashik 20/ Panaji /

24 63 Pathankot / Patiala / Pithoragarh / Porbandar / Port Blair 13.65/ Pune 18.5/ Ranchi / Sagar / Samba 32.55/ Shiliguri / Shillong / Shimla 31.1/ Silchar / Silvassa 20.25/ Sirsa / Srinagar / Surat 21.2/ Tezpur / Thiruvananthapuram / Udaipur 24.65/ Udhampur / Umaria 23.55/ Vadodara / Varanai / Vishakhapatnam / Auth: 24

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