Types of Solar Collectors

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    .and its many uses

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    SOLAR ENERGY

    A FEW FACTS

    Every day the earth receives thousands of timesmore energy from the sun than is consumed in all

    other resources.

    The sunlight falling on a typical house can providefrom 1/3 to 1/2 of the heating needs of that house.

    Today solar energy accounts for only 3% of thetotal renewable energy consumed in world.

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    Characteristics of Isolation

    Isolation is the amount of solarradiation reaching the earth. Alsocalled Incident Solar Radiation.

    The suns energy is created fromthe fusion of hydrogen nuclei intohelium nuclei.

    Components of Solar Radiation: Direct radiation

    Diffuse radiation

    Reflect radiation

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    SOLAR HEATING TODAY

    Used mostly forheating pools anddomestic hot water

    (DHW)

    Two types of solarheating systems:

    Active Solar HeatingSystemPassive Solar Heating

    System

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    ACTIVE SOLAR HEATING

    SYSTEMA system that uses

    water or air that the sun

    has heated and is thencirculated by a fan orpump.

    Two Types:

    Flat Plate CollectorsEvacuated-tube Collectors

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    FLAT PLATE COLLECTORS

    A thin flat metal plate isused to absorb the sunsradiation.

    Tubes carry water intothe absorber plate whereit is heated by the sunand sent to a pump or

    fan into storage anddistributed from there tothe living space.

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    Evacuated-tube CollectorsAn evacuated-tube collector consists of parallel rows of glass tubes connected toa header pipe. Each tube has the air removed from it to eliminate heat lossthrough convection and radiation.

    Temperatures, in the range 170F (77C) to 350F (177C) quite expensive, withunit area costs typically about twice that of flat-plate collectors.

    They can also be an effective alternative to flat-plate collectors for domesticspace heating, especially in regions where it is often cloudy. For domestic hot

    water heating, flat-plate collectors tend to offer a cheaper and more reliableoption.

    Evacuated-tube collectors fall into two main groups.

    Direct-flow evacuated-tube collectors

    Heat pipe evacuated-tube collectors

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    Direct-flow evacuated-tube collectors

    These consist of a group of glass tubes inside each of which is a flat or curvedaluminium fin attached to a metal (usually copper) or glass absorber pipe. Thefin is covered with a selective coating that absorbs solar radiation well but slowdown radiative heat loss. The heat transfer fluid is water and circulates throughthe pipes, one for inlet fluid and the other for outlet fluid. Direct-flow evacuatedtube collectors come in several varieties distinguished by the arrangement ofthese pipes.

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    Heat pipe evacuated-tube collectors

    These consist of a metal (copper) heat pipe, to which is

    attached a black copper absorber plate, inside a vacuum-sealedsolar tube. The heat pipe is hollow and the space inside, likethat of the solar tube, is evacuated. The reason for evacuatingthe heat pipe, however, is not insulation but to promote achange of state of the liquid it contains. Inside the heat pipe isa small quantity of liquid, such as alcohol or purified water plusspecial additives. The vacuum enables the liquid to boil (i.e.turn from liquid to vapor) at a much lower temperature than itwould at normal atmospheric pressure. When solar radiation

    falls the surface of the absorber, the liquid within the heat tubequickly turns to hot vapor rises to the top of the pipe. Water, orglycol, flows through a manifold and picks up the heat, whilethe fluid in the heat pipe condenses and flows back down thetube for the process to be repeated.

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    Active Solar Water Heating Systems

    Types of active solar water heating systems:

    Direct circulation systems

    Pumps circulate household water through the collectors and intothe 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 thenflows into the home. They are popular in climates prone to freezingtemperatures.

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    The direct pumped system, illustrated in, has one or more solar

    energy collectors installed on the roof and a storage tanksomewhere below, usually in a garage or utility room. A pumpcirculates the water from the tank up to the collector and backagain. This is called a direct (or open loop) system because thesun's heat is transferred directly to the potable water circulating

    through the collector tubing and storage tank; no anti-freezesolution or heat exchanger is involved.

    Direct Pumped System

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    Indirect Pumped SystemThis system design is common in northern climates, where freezingweather occurs more frequently. An antifreeze solution circulates through

    the collector, and a heat exchanger transfers the heat from the antifreezesolution to the tank water.

    The brain of the system is a differential controller.

    The fluid used in this system is a mixture of distilled water and antifreezesimilar to that used in automobiles. This type of fluid freezes only atextremely low temperatures so the system is protected from damagecaused by severe cold.

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    Closed Loop Drainback

    When the pump turns on, the distilled water is circulated from thereservoir back through the collector and heat exchanger, passing heat to

    the potable water in the solar tank. When the pump shuts off again, thedistilled water drains back into the reservoir. The collector must thereforealways be higher than the storage tank, and there must be sufficientcontinuous slope in the piping to ensure against freezing.

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    Passive Solar Water Heating Systems

    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 twobasic types of passive systems

    Batch: This is as simple as a water heater gets. It's just one or more water tanksinside a solar collector (no tubes in this one). The water warms up right inside thetank, and either gravity or natural convection (the tendency of hot water to rise)moves water from the tank to a home's pipes.

    Thermosiphon: The water tank is separate from the solar collector. Cold watermoves through the tubes of a solar collector, and natural convection pumps theresulting hot water into a storage tank. From the storage tank, the water travels intothe home's water pipesWater flows through the system when warm water rises as cooler water sinks. Thecollector must be installed below the storage tank so that warm water will rise intothe tank. These systems are reliable, but contractors must pay careful attention tothe roof design because of the heavy storage tank. They are usually more expensivethan integral collector-storage passive systems.

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    Batch ICS systems do not involve pumps and do no demand a separated storage

    tank, or anti-freezing, heat exchanger, valves, sensors. A batch panel is typicallyvery similar to a flat-plate collector, with a greater depth of at least 6 inches (15cm). The water is heated directly in the collector (they are open-loop systems) andno pump is used to move the water (they are passive systems).

    Their working principle is very basic:

    whenever the homeowner demands the hot water stored in the batch system, thewater pressure moves the hot water on the top of the batch tank (hot water risesnaturally to the top of the batch tank).

    Batch Water Heaters

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    PASSIVE SOLAR HEATINGSYSTEMS The house itself acts as the solar collector

    and storage facility.

    No pumps or fans are used.

    This system makes use of the materials ofthe house to store and absorb heat.

    Three Types: Direct-Gain

    Indirect-Gain

    Attached Greenhouse

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    DIRECT-GAIN

    Large south facingwindows that let in thesunlight.

    Thermal mass is usedto absorb the radiation.

    At night the absorbed

    heat is radiated backinto the living space.

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    INDIRECT-GAIN

    Collects and stores thesolar energy in one partof the house and use

    natural heat transfer todistribute heat to the restof the house.

    Popular method is to usea Trombe Wall which is a

    massive black masonrythat acts as a solarcollector and a heatstorage medium.

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    ATTACHED GREENHOUSE

    Uses a combination ofDirect and Indirect-Gainsystems that use waterdrums and a masonry flooras heat storage in the

    attached greenhouse.

    Thermosiphoning can usedirect-gain from the flow ofair created by thedifference in pressure

    between the less densewarmer air of the room andthe cooler air near theground.

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    THERMAL ENERGYSTORAGE Solar energy heating systems must be able

    to store energy for night time use and forcloudy days. Different materials absorbdifferent amounts of heat.

    Depending on the weather and the amountof thermal energy stored will determinehow long a house can continue to beheated by the stored solar energy.

    Phase-change material can be used to addadditional heat to the living space.

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    This House Uses an Active AirSystem

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    How cells are built

    The Photoelectric Effect

    Pros and Cons of PV

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    4 types of PV cells

    SelectiveEmitter Cell (SEC)

    Emitter wrap- through cells (EWC)

    Thin Film Photovoltaic

    Single Crystal Silicon Cells

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    Single-Crystal Silicon CellConstruction

    The majority of PV cells in use are the single-crystal silicontype.

    Silica (SiO2) is the compound used to make the cells. It isfirst refined and purified, then melted down and re-solidifiedso that it can be arranged in perfect wafers for electric

    conduction. These wafers are very thin. The wafers then have either Phosphorous or Boron added to

    make each wafer either a negative type layer or a positivetype layer respectively. Used together these two typestreated of crystalline silicon form the p-n junction which is theheart of the solarelectrical reaction.

    Many of these types of cells are joined together to makearrays, the size of each array is dependant upon the amountof sunlight in a given area.

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    How Does A Cell Become A Module?

    A solar cell is the basic buildingblock of a PV system.

    A typical cell produces .5 to 1V ofelectricity.

    Solar cells are combined togetherto become modules or if largeenough, known as an array.

    A structure to point the modulestowards the sun is necessary, aswell as electricity converters,which convert DC power to AC.

    All of these components allow thesystem to power a water pump,appliances, commercial sites, oreven a whole community.

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    The Photoelectric Effect

    The photoelectric effect relies onthe principle that whenever lightstrikes the surface of certainmetals electrons are released.

    In the p-n junction the n-type wafer

    treated with phosphorus has extraelectrons which flow into the holesin the p-type layer that has beentreated with boron.

    Connected by an external circuitelectrons flow from the n-side tocreate electricity and end up in thep-side.

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    Photoelectric Effect

    A picture of an typical silicon PV cell

    Now a short video:

    http://www.eere.energy.gov/solar/multimedia.html

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    Sunlight is the catalyst of the reaction.

    The output current of this reaction is DC (direct) and theamount of energy produced is directly proportional to theamount of sunlight put in.

    Cells only have an average efficiency of 30%

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    Pros and Cons of SolarElectricity

    Expensive to produce because of the high cost of semi- conductingmaterials, which could be avoided by reducing manufacturing costs.The PV Manufacturing Research and Development Project focuseson increasing manufacturing capacity so that the cost ofmanufacturing will decrease. They aim to achieve break even costs.

    However, solar energy contributes positively to the nations energy

    security because it is produced domestically, reducing reliance onenergy imports.

    The industry is still relatively new and extremely hi tech allowing forthe creation of more jobs in the American market.

    The government has many incentives program which vary fromstate to state, but they exist to encourage investment in forms of

    alternative energy. Does not require the transportation of hazardous materials across

    country.

    Sunlight is a free abundant source!

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    Pros and Cons cont.

    PV can be designed for a variety ofapplications

    No noise or air pollution

    Require minimal maintenance and havelong service life times.

    Power can be either centralized inindividual homes or distributed byelectrical companies.

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    Stand-Alone Photovoltaic Systems

    Grid-connected

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    BREAKDOWN

    PV systems are like any other electrical power generating systems,except the equipment used to generate the power is different.

    Specific components required, and may include major componentssuch as a DC-AC power inverter, batteries, auxiliary energysources, sometimes the specified electrical load (appliances),

    wiring, surge protection and other hardware. Batteries are often used in PV systems for the purpose of storing

    energy produced by the PV array during the day, and to supply it toelectrical loads as needed (during the night and periods of cloudyweather). Also to keep the system at full operational power

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    Grid-connected or Utility-Connected

    Grid-connected or utility-interactive PV systems are designed tooperate in parallel with and interconnected with the electric utilitygrid.

    These system contain an inverter, called a power conditioning unit(PCU) which converts the DC power produced by the PV array into

    AC power consistent with the voltage and power qualityrequirements of the utility grid.

    A bi-directional interface allows the AC power produced by the PVsystem to either supply personal electrical loads, or return powerback to the grid when the PV system output is greater than thepersonal demand.

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    Stand-Alone PV Systems

    Stand-alone PV systems are designed to operate independent ofthe electric utility grid

    Supply DC and/or AC electrical loads

    The simplest type of stand-alone PV system is a direct-coupledsystem, where the DC output of a PV module or array is directly

    connected to a DC load Since there are no batteries involved in direct load systems, stand-

    alone PV systems are suitable for such processes as heating andpumping water, ventilation fans, etcAlthough they can only work

    in the day.

    Stand-Alone systems may also power AC loads such as batteries.Like the AC adapter which powers your laptop.

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    The Grid and All of Its Glory

    Net metering allows a home or business owner to sell electricitygenerated by PV modules to the utility grid. This benefits both theconsumer, and in some cases the utility.

    The electric meter will run backward when there is an excess ofelectricity needed to power a building.

    A safety measure cuts off the PV system from the grid in case of anemergency.

    At the End of the Month, the Consumer will reek the benefits.

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    Benefits to The Economy, Environment,You, and Me

    Americans yearn for reliable,clean, abundant, affordableenergy, and safe energy.

    Can prevent catastrophessuch as the blackout on Aug14, 2003. Businesses are inturn investing in solar to avoid

    these instances Solar electric power systems

    can be easily sited at thepoint of use with noenvironmental impact.

    The current U.S. solarindustry employs some20,000 men and women inhigh-value, high-tech jobs,representing about 300companies, universities, andutilities

    Solar thermal collector shipmentssurged 34% in 2001 to 11.2 millionsquare feet.

    The total revenue for all shipments ofsolar thermal collectors was $32.4million in 2001, up 18% from 2000.

    Nearly 73% of all solar collectors arefor pool-heating applications.Solar water heaters comprise theremaining 27% of U.S. solar thermalapplications.

    In 2001, the overall value of PV celland PV module shipments rose by13% to $305 million.

    In terms of price per peak megawatt,prices have remained stable at $2.46for PV cells and $3.42 for PV modules.

    Photovoltaic (PV) systems have very little impact on the environment

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    Photovoltaic (PV) systemshave very little impact on the environment,making them one of the cleanest power-generating technologies available .

    Solar power produces no air pollution.

    Solar power produces no greenhouse gases, so it does not contribute to

    global warming.

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    Production

    Combinations of haz and non-hazmaterials + High temperatures = highenvironmental cost

    Cost decline as companies dependmore on solar for production ofcells/modules

    Lif

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    Life

    Average 20-30 years

    Efficiency decrease 1% a year.

    Research on manufacturing and output

    efficiency and recycling ongoing.

    Payback or energy break even - 15years.

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    After life

    Waste generation lag due to life oftechnology

    Heavy metals and toxic gases produced

    in breakdown. High temperatures

    Example of Progressive

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    Example of Progressivepolicy

    EU End of Life of Vehicles Policy.

    PV Industry has a pro-active approachto energy saving/environmental benefit

    increase etc. Policy can be created like ELV to

    encourage manufacturers to incorporate

    breakdown into production.

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    Things to consider when looking attechnologies

    Payback or breakeven is important(Energy produced by technology -energy used in production )

    Less hazardous materials.

    More easily taken apart if constructedwith several detachable components

    which could be recycled or smelted.

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    Solar Energy Organizations

    International solar energy society (ISES) Founded in 1954

    A UN accredited non-government

    organization Exists in over 50 countries

    Promoting international development ofsolar energy

    Holds a biannual solar world congress, thenext will be held next year in OrlandoFlorida

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    American Solar Energy SocietyThe American Chapter of the International

    Energy Society-Located in Boulder CO- Nations Largest andOldest Membership Organization forRenewable Energy

    -Sponsors the National Solar EnergyConference: Held July 10-14, Portland OR-Publishes the Bimonthly Magazine SolarToday-Organizes the Annual National Solar Tour-Organizes the Solar Action Network

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    Vermont Based Solar Providers

    Vermont Solar Businesses that are Members ofSEBANE:

    Northern Power SystemsNorthern Power Systems designs, builds and

    installs high reliability electric power systems.Northern has installed over 800 systemsworldwide in the past 25 years, earning areputation for delivering top-quality energysolutions. Northern provides photovoltaic, wind

    and wind/diesel hybrid power for commercial,industrial, institutional and government clients.

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    Vermont Based Solar Providers Solar Works, Inc.

    Since 1980, Solar Works, Inc., has provided renewable energyservices and equipment to government agencies, utilities, privatebusinesses, homeowners, and not-for-profit organizations in theUnited States and overseas. As a full-service renewable energyfirm, Solar Works maintains sales offices in California, Connecticut,Maine, Maryland, Massachusetts, New Hampshire, New Jersey,New York, Rhode Island, and Vermont. Our experience includes:program development, project management, and the design andinstallation of Photovoltaic (Solar Electric or PV) Systems, SolarThermal Systems (both active and passive), High-efficiency

    Lighting and Heating systems, and small-scale Wind Turbines.

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    Vermont Based Solar Companies Sunnyside Solar, Inc.

    Sunnyside Solar, Inc. is a full service photovoltaic companyspecializing in line-tie and stand alone photovoltaic systems.Design, & engineering, equipment sales, full service &installation capabilities. Educational programs seminars andworkshops. Sunnyside Solar, Inc. The gentle electriccompany. We bring good things from light!

    Sunrise Solar ServiceSunrise Solar Service installs, sells, and services domestichot water systems, pool heating, water pumping, lighting

    systems, and system components and supplies.

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    Sources

    http://www.eere.energy.gov/solar/photovoltaics.html

    http://www.fsec.ucf.edu/pvt/pvbasics/index.htm60

    http://www.brookes.ac.uk/eie/elv.htm

    http://www.environmentaldefense.org/documents

    /894_GC_takeback.htm

    http://www.eere.energy.gov/solar/photovoltaics.htmlhttps://webmail.uvm.edu/horde/util/go.php?url=http%3A%2F%2Fwww.brookes.ac.uk%2Feie%2Felv.htm&Horde=b880cae8c7a92363abd32e5811c7f74fhttps://webmail.uvm.edu/horde/util/go.php?url=http%3A%2F%2Fwww.environmentaldefense.org%2Fdocuments%2F894_GC_takeback.htm&Horde=b880cae8c7a92363abd32e5811c7f74fhttps://webmail.uvm.edu/horde/util/go.php?url=http%3A%2F%2Fwww.environmentaldefense.org%2Fdocuments%2F894_GC_takeback.htm&Horde=b880cae8c7a92363abd32e5811c7f74fhttps://webmail.uvm.edu/horde/util/go.php?url=http%3A%2F%2Fwww.environmentaldefense.org%2Fdocuments%2F894_GC_takeback.htm&Horde=b880cae8c7a92363abd32e5811c7f74fhttps://webmail.uvm.edu/horde/util/go.php?url=http%3A%2F%2Fwww.environmentaldefense.org%2Fdocuments%2F894_GC_takeback.htm&Horde=b880cae8c7a92363abd32e5811c7f74fhttps://webmail.uvm.edu/horde/util/go.php?url=http%3A%2F%2Fwww.brookes.ac.uk%2Feie%2Felv.htm&Horde=b880cae8c7a92363abd32e5811c7f74fhttp://www.eere.energy.gov/solar/photovoltaics.html
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    Contact Information

    Northern Power SystemsJito ColemanPresidentP.O. Box 999182 Mad River ParkWaitsfield, VT 05673-0999

    Solar Works, Inc.Leigh SeddonPresident64 Main StreetMontpelier, VT 05602

    Sunnyside Solar, Inc.Richard Gottlieb1014 Green River RoadGuilford, VT 05301-8117

    Sunrise Solar Service

    Ed ButlerP.O. Box 129454 Hunt RoadRandolph, VT 05060