11 March 2013NCES Lecture Applications of Solar Energy Subject : NCES Branch : Civil (Sem – 4)

11 March 2013NCES Lecture SOLAR COLLECTORS  Types of collectors Stationary Sun tracking  Applications Solar water heating Solar space heating and cooling Refrigeration Industrial process heat Desalination Solar thermal power systems

11 March 2013NCES Lecture Types of solar collectors MotionCollector type Absorber type Concentration ratio Indicative temperature range (°C) Stationary Flat plate collector (FPC) Flat Evacuated tube collector (ETC) Flat Compound parabolic collector (CPC)Tubular Single-axis tracking Linear Fresnel reflector (LFR) Tubular Parabolic trough collector (PTC) Tubular Cylindrical trough collector (CTC) Tubular Two-axes tracking Parabolic dish reflector (PDR) Point Heliostat field collector (HFC) Point Note: Concentration ratio is defined as the aperture area divided by the receiver/absorber area of the collector.

11 March 2013NCES Lecture Solar energy applications and type of collectors used ApplicationSystemCollector Solar water heating Thermosyphon systems Integrated collector storage Direct circulation Indirect water heating systems Air systems Passive Active FPC CPC FPC, CPC ETC FPC Space heating and cooling Space heating and service hot water Air systems Water systems Heat pump systems Absorption systems Adsorption (desiccant) cooling Mechanical systems Active FPC, CPC ETC FPC FPC, CPC ETC PDR Solar refrigeration Adsorption units Absorption units Active FPC, CPC ETC

11 March 2013NCES Lecture Solar energy applications and type of collectors used ApplicationSystemCollector Industrial process heat Industrial air and water systems Steam generation systems Active FPC, CPC ETC PTC, LFR Solar desalination Solar stills Multi-stage flash (MSF) Multiple effect boiling (MEB) Vapour compression (VC) Passive Active - FPC, CPC ETC Solar thermal power systems Parabolic trough collector systems Parabolic tower systems Parabolic dish systems Solar furnaces Solar chemistry systems Active PTC HFC PDR HFC, PDR CPC, PTC, LFR

 Active System: forced circulation system used mechanical pump to circulate hot water  Passive system: Density difference of hot & cold water provides driving force to setup natural convection for circulation of water 11 March 2013NCES Lecture

TEI Patra: 3-18 July 2006Intensive program: ICT tools in PV-systems Engineering Solar Water Heating Systems Thermosyphon systems Integrated collector storage systems Direct circulation systems Indirect water heating systems Air systems 11 March 2013NCES Lecture

11 March 2013NCES Lecture Schematic diagram of a thermosyphon solar water heater Auxiliary Storage tank Hot water outlet Cold water inlet Main Components Flat plate collector Hot water tank Support structure, piping Cold water tank

11 March 2013NCES Lecture Thermosyphon systems (passive)  Thermo syphon systems heat potable water or heat transfer fluid and use natural convection to transport it from the collector to storage.  The water in the collector expands becoming less dense as the sun heats it and rises through the collector into the top of the storage tank.  There it is replaced by the cooler water that has sunk to the bottom of the tank, from which it flows down the collector.  The circulation continuous as long as there is sunshine.  Since the driving force is only a small density difference larger than normal pipe sizes must be used to minimise pipe friction.  Connecting lines must be well insulated to prevent heat losses and sloped to prevent formation of air pockets which would stop circulation.  Electric heater – to heat water in cloudy climate

11 March 2013NCES Lecture Typical thermosyphon solar water heater

11 March 2013NCES Lecture Laboratory model

11 March 2013NCES Lecture Application on inclined roof-1

11 March 2013NCES Lecture Application on inclined roof-2

11 March 2013NCES Lecture Application on inclined roof-3

11 March 2013NCES Lecture Multi-residential application

11 March 2013NCES Lecture Pressurized system on inclined roof

11 March 2013NCES Lecture Direct circulation system

11 March 2013NCES Lecture Direct circulation systems (active)  In direct circulation systems a pump is used to circulate potable water from storage to the collectors  When there is enough available solar energy to increase its temperature and then return the heated water to the storage tank until it is needed.  As a pump circulates the water, the collectors can be mounted either above or below the storage tank.

11 March 2013NCES Lecture Direct circulation systems (active)  Water from storage tank - pumped through array of solar collector  Water get heated in collector – flow back to storage tank  Check valve (NRV) – to prevent reverse flow of hot water through cold solar collector in night  Pump – controlled by electronic controller starts at pre-determined temperature difference

11 March 2013NCES Lecture Direct or forced circulation type domestic SWH  In this system only the solar panels are visible on the roof.  The hot water storage tank is located indoors in a plantroom. The system is completed with piping, pump and a differential thermostat.  This type of system is more appealing mainly due to architectural and aesthetic reasons but also more expensive.

11 March 2013NCES Lecture Drain-down system When a freezing condition or a power failure occurs, the system drains automatically by isolating the collector array and exterior piping from the make- up water supply and draining it using the two normally open (NO) valves

11 March 2013NCES Lecture Direct or forced circulation type domestic SWH  To protect system due to freezing Drain water from collector Use antifreeze

11 March 2013NCES Lecture Force circulation system-1

11 March 2013NCES Lecture Air systems  Air systems are indirect water heating systems that circulate air via ductwork through the collectors to an air-to-liquid heat exchanger.  In the heat exchanger, heat is transferred to the potable water, which is also circulated through the heat exchanger and returned to the storage tank.  The main advantage of the system is that air does not need to be protected from freezing or boiling, is non-corrosive, and is free.  The disadvantages are that air handling equipment (ducts and fans) need more space than piping and pumps, air leaks are difficult to detect, and parasitic power consumption is generally higher than that of liquid systems.

11 March 2013NCES Lecture Air system

TEI Patra: 3-18 July 2006Intensive program: ICT tools in PV-systems Engineering Solar Space Heating and Cooling Space Heating and Service Hot Water Air systems Water systems 11 March 2013NCES Lecture

11 March 2013NCES Lecture Solar Space Heating and Cooling  The components and subsystems discussed so far may be combined to create a wide variety of building solar heating and cooling systems.  Active solar space systems use collectors to heat a fluid, storage units to store solar energy until needed, and distribution equipment to provide the solar energy to the heated spaces in a controlled manner.  The load can be space cooling, heating, or a combination of these two with hot water supply.  In combination with conventional heating equipment solar heating provides the same levels of comfort, temperature stability, and reliability as conventional systems.  Passive system : collection, storage and distribution done by natural means

11 March 2013NCES Lecture Space Heating and Service Hot Water  It is useful to consider solar systems as having five basic modes of operation, depending on the conditions that exist in the system at a particular time: If solar energy is available and heat is not needed in the building, energy gain from the collector is added to storage. If solar energy is available and heat is needed in the building, energy gain from the collector is used to supply the building need. If solar energy is not available, heat is needed in the building, and the storage unit has stored energy in it, the stored energy is used to supply the building need. If solar energy is not available, heat is needed in the building, and the storage unit has been depleted, auxiliary energy is used to supply the building need. The storage unit is fully heated, there are no loads to met, and the collector is absorbing heat-relief heat.

11 March 2013NCES Lecture Air systems  A schematic of a basic solar heating system using air as the heat transfer fluid, with pebble bed storage unit and auxiliary heating source is shown in next slide.  The various modes of operations are achieved by appropriate positioning of the dampers. In most air systems it is not practical to combine the modes of adding energy to and removing energy from storage at the same time.  Auxiliary energy can be combined with energy supplied from collector or storage to top-up the air temperature in order to cover the building load.  It is possible to bypass the collector and storage unit when auxiliary alone is being used to provide heat.  Dampers – top of glass cover to allow excess heat to escape when heating is not required

11 March 2013NCES Lecture Schematic of basic hot air system

11 March 2013NCES Lecture Detail schematic of a solar water heating system

11 March 2013NCES Lecture Active Hot Water space heating systems  When used for both space and hot water production this system allows independent control of the solar collector-storage and storage-auxiliary-load loops as solar-heated water can be added to storage at the same time that hot water is removed from storage to meet building loads.  Usually, a bypass is provided around the storage tank to avoid heating the storage tank, which can be of considerable size, with auxiliary energy.

11 March 2013NCES Lecture Solar Refrigeration  Solar cooling can be considered for two related processes: to provide refrigeration for food and medicine preservation and to provide comfort cooling.  Absorption systems are similar to vapour- compression air conditioning systems but differ in the pressurisation stage.  The most usual combinations of fluids include lithium bromide-water (LiBr-H 2 O) where water vapour is the refrigerant and ammonia-water (NH 3 -H 2 O) systems where ammonia is the refrigerant.

11 March 2013NCES Lecture Absorption systems  The pressurisation is achieved by dissolving the refrigerant in the absorbent, in the absorber section.  Subsequently, the solution is pumped to a high pressure with an ordinary liquid pump.  The addition of heat in the generator is used to separate the low-boiling refrigerant from the solution. In this way the refrigerant vapour is compressed without the need of large amounts of mechanical energy that the vapour-compression air conditioning systems demand.

11 March 2013NCES Lecture Basic principle of the absorption air conditioning system Condenser Evaporator Generator Heat exchanger Absorber High pressure Low pressure QCQC QGQG QEQE QAQA Cooling water Source heat Chilled water

TEI Patra: 3-18 July 2006Intensive program: ICT tools in PV-systems Engineering Industrial Process Heat 11 March 2013NCES Lecture

11 March 2013NCES Lecture Industrial Process Heat  The central system for heat supply in most factories uses hot water or steam at a medium temperature of about 150°C.  Hot water or low pressure steam at medium temperatures can be used either for preheating of water (or other fluids) used for processes (washing, dyeing, etc.) or for steam generation or by direct coupling of the solar system to an individual process.  In the case of water preheating, higher efficiencies are obtained due to the low input temperature to the solar system, thus low- technology collectors can work effectively.

11 March 2013NCES Lecture Possibilities of combining the solar system with the existing heat supply Conventional boiler and steam generator Process Return water Central steam supply Make-up water Solar collector applied to a particular process Solar collector used for make-up water preheating Solar collector used for steam generation Pump

11 March 2013NCES Lecture PTCs for water heating

11 March 2013NCES Lecture Solar steam generation systems  Parabolic trough collectors are frequently employed for solar steam generation because relatively high temperatures can be obtained without any serious degradation in the collector efficiency.  Low temperature steam can be used in industrial applications, sterilisation, and for powering desalination evaporators.  Three methods have been employed to generate steam using parabolic trough collectors: The steam-flash concept. The direct or in-situ concept. The unfired-boiler concept.

TEI Patra: 3-18 July 2006Intensive program: ICT tools in PV-systems Engineering Solar Desalination Systems 11 March 2013NCES Lecture

11 March 2013NCES Lecture Solar Desalination Systems  Water is one of the most abundant resources on earth, covering three ‑ fourths of the planet's surface.  About 97% of the earth's water is salt water in the oceans; 3% of all fresh water is in ground water, lakes and rivers, which supply most of human and animal needs.  The only nearly inexhaustible sources of water are the oceans  Their main drawback, however, is their high salinity.  It would be attractive to tackle the water- shortage problem with desalination of this water.

11 March 2013NCES Lecture Desalination processes PHASE-CHANGE PROCESSESMEMBRANE PROCESSES 1. Multi-stage flash (MSF) 2. Multiple effect boiling (MEB) 3. Vapour compression (VC) 4. Freezing 5. Humidification/Dehumidification 6. Solar stills - conventional stills - special stills - wick-type stills - multiple-wick-type stills 1. Reverse osmosis (RO) - RO without energy recovery - RO with energy recovery (ER-RO) 2. Electrodialysis (ED) Desalination can be achieved by using a number of techniques. These may be classified into the following categories: - phase-change or thermal processes; and - membrane or single-phase processes.

11 March 2013NCES Lecture Solar Stills

TEI Patra: 3-18 July 2006Intensive program: ICT tools in PV-systems Engineering Solar Power systems 11 March 2013NCES Lecture

11 March 2013NCES Lecture Solar Thermal Power  Three types of systems belong to this category: Parabolic trough collector system Central receiver system Dish collector system  The process of conversion of solar to mechanical and electrical energy by thermal means is fundamentally similar to the traditional thermal processes.  The solar systems differ from the ones considered so far as these operate at much higher temperatures.

11 March 2013NCES Lecture Schematic of a solar-thermal conversion system

11 March 2013NCES Lecture Typical Schematic of SEGS plants

11 March 2013NCES Lecture Parabolic Trough System

11 March 2013NCES Lecture Parabolic trough collectors

11 March 2013NCES Lecture Parabola detail

11 March 2013NCES Lecture Receiver detail

11 March 2013NCES Lecture Central receiver system

11 March 2013NCES Lecture Tower detail

11 March 2013NCES Lecture Heliostat detail

11 March 2013NCES Lecture Central receiver-1

11 March 2013NCES Lecture Central receiver-2

11 March 2013NCES Lecture Central receiver-3

11 March 2013NCES Lecture Central receiver-4

11 March 2013NCES Lecture Central receiver-5

11 March 2013NCES Lecture Central receiver-6

11 March 2013NCES Lecture Central receiver-7

11 March 2013NCES Lecture Central receiver-8

TEI Patra: 3-18 July 2006Intensive program: ICT tools in PV-systems Engineering Solar energy should be given a chance if we want to protect the environment. We own it to our children, our grandchildren and the generations to come. Thank you for your attention, any questions please…. 11 March 2013NCES Lecture