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Solar Energy Introduction MECH 430 Queen’s University, Kingston, ON, Canada Renewable Energy Renaissance • • • • • • Wind Energy Solar Energy Water Energy Earth Energy Bio Energy Energy from Waste Why Renewable Energy? • Environment • Energy Supply and security • Cost Motivation Global Warming - global warming is the increase in the average temperature of Earth’s near-surface air and oceans since the mid-20th century and its projected continuation - evidence for warming of the climate system includes observed increases in global average air and ocean temperatures, widespread melting of snow and ice and rising global average sea level - the most common measure of global warming is the trend in globally averaged temperature near the earth’s surface Solar Collector Technology Solar Resource The Solar Energy Resource The Solar Energy Spectrum The Solar Energy Resource here for Thursday Dec 3/15 • • • • • • Varies over day and year Generally non-dispatchable Depends on the orientation Solar constant 1360 W/m2 (Extraterrestrial) Peak Power ~ 1kW/m2 Average Energy ~ 4 kWh/m2 day (Kingston) Average Solar Radiation 7 5 4 3 2 1 De c No v Oc t Se pt Au g Ju l Ju n Ma y Ap r Ma r Fe b 0 Ja n 2 H (kWh/m day) e.g., for 60 roof we have 240 kWh/day or 7200 kWh/month 0 30 45 60 6 m2 Collector Orientation Effects of Receiving Surface Tilt (fixed orientation) Tracking vs stationary Tracki ng From “Solar Engineering of Thermal Processes”, Duffie & Beckman Solar Energy Availability From “Planning and Installing Solar Thermal Systems”, James & James/Earthscan, London, UK The amount of solar energy available on the earth depends on the geographical latitude and the time of day and year at a given location. Average Solar Energy The average annual global horizontal solar energy is greater at lower latitudes, however this effect may be reduced by tilting the receiver when at higher latitudes Monthly solar irradiation (kWh/m2 per day on a horizontal surface) around the world From “Planning and Installing Solar Thermal Systems”, James & James/Earthscan, London, UK The Solar Energy Resource How does Canada Compare? Solar Radiation in Miami and Toronto on slope=latitude 0.7 Miami Totonto Toronto receives approx. 80% of solar radiation as in Miami, and Approx. 96% of solar radiation as in Miami from April to September. Monthly total solar in GJ 0.6 0.5 0.4 0.3 0.2 0.1 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Solar Energy Conversion • Passive solar: – Direct gain – high performance fenestration/thermal mass – Solar heating and daylighting – Good architecture and energy conservation • Photovoltaics: the production of electricity – Grid connected/stand alone – Building integrated PV – “Net Zero” buildings • Solar Thermal: solar heating – space and water heating/cooling – Packaged SDHW – Solar boosted ground source heat pump • PV Thermal/Hybrid systems Passive Solar Heating Summer Good architecture? The judicious use of south glazing coupled with appropriate shading and thermal mass. Winter Attached Sun Space Solar Thermal Energy Photovoltaics Energy Systems Utility-Scale Grid-Connected PV Kingston Building FIT program! (or unfit Program ?) Solar Energy Photovoltaics Theory and Application The PV Effect (http://inventors.about.com) 1904:Einstein published his paper on the photoelectric effect. 1923: Albert Einstein received the Nobel Prize for his theories explaining the photoelectric effect. 1954: The PV effect in Cd was reported; primary work was performed by Rappaport, Loferski and Jenny at RCA. Bell Labs researchers Pearson, Chapin, and Fuller reported their discovery of 4.5% efficient silicon solar cells; this was raised to 6% only a few months later (by a work team including Mort Prince). Photovoltaic Systems - the term “photovoltaic” refers to the direct generation of electricity by solar irradiation photo = light voltaics = electricity photovoltaics = electricity from light abbreviated as “PV” Types of Silicon Solar Cells - the three types of silicon cells are: • mono-crystaline • poly-crystaline • amorphous mono-crystaline polycrystaline amorphous Source: Alternative Energy Systems and Applications, B.K. Hodge Photovoltaic Cell Fundamentals - photovoltaic cells are made of a semiconductor material - the most common semiconductor used is silicon - the two layers of silicon that constitute a silicon-based PV cell are modified (doped) to more likely: 1) loose electrons 2) produce holes in the molecular structure where electrons can reattach + silicon-based PV cell Photovoltaic Cell Fundamentals - as an example, in one PV cell design, the upper or n-type layer is doped with phosphorus with 5 valence electrons while the lower or p-type layer is doped with boron, which has 3 valence electrons (recall that the silicon atom has 4 valence electrons in its outer shell) - if the incident photon is energetic enough to dislodge a valance electron (from the depletion zone / electric field), the electron will jump to the conduction band and initiate a current flow Prof. C. A. Cruickshank, Carleton University Current Density Ratio and Power Ratio vs. Voltage - I-V Characteristics Curve Prof. C. A. Cruickshank, Carleton University Standard Test Conditions and Temperature and Irradiance Effects - the efficiency η of a solar cell is defined as: the power Pmax produced by the cell at the maximum power point under standard test conditions the power of the radiation incident upon it - most frequent conditions are: irradiance 100 mW/cm2, standard reference AM1.5 spectrum, and temperature 25oC - in practical applications, however, solar cells do not operate under standard conditions - the two most important effects that must be allowed for are due to the variable temperature and irradiance Efficiency of PV Optimal Running Condition - although it is desired to operate the cell at the maximum power point, this may not easily be realize in practice - a simpler but less efficient solution is to operate the cell at a constant voltage below the voltage of maximum power point - if the operating voltage remains in the linear part of the I-V characteristic, temperature will have little effect on the power output - the power delivered to the load will therefore be proportional to the short circuit current and thus also irradiance Source: Solar Electricity, Tomas Markvart Prof. C. A. Cruickshank, Carleton University The price of solar photovoltaic cells has dropped 99% in the past quarter century. So in an increasing number of markets around the country, solar is at or very close to grid parity, (http://thinkprogress.org) the levelized cost of electricity More and more countries and regions will reach residential grid parity. Germany, Spain, Italy, Australia and Hawaii were among the first to do so. Photovoltaic Components - the basic building block of a PV system is the individual solar cell - individual cells are assimilated into ‘strings’ which make up a module; modules are then assembled in arrays - modules are constructed by placing PV cells in series and parallel arrangements glass cover to protect cells various frame and backing materials to facilitate mounting Prof. C. A. Cruickshank, Carleton University Photovoltaic Components - series and parallel configurations of solar cells follow the same rules as series and parallel DC circuits - for identical components placed in series, the voltages add at constant current (multiple cells in series to increase operating voltage) - for identical components placed in parallel, the currents add at constant voltage (multiple strings in parallel increase current – used to power up to several MW) series Source: Alternative Energy Systems and Applications, B.K. Hodge parallel EXAMPLE Photovoltaic cells are to be arranged to provide an output of 12 V and a power of 120 W. If the voltage and current at maximum power are 0.493 V and 5.13 A (V*I = 2.53 W), recommend an arrangement that meets the specifications. SOLUTION - the number of cells required for 120 W is number of cells = 120 W / (2.53 W/cell) = 47.2 cells - to provide the correct voltage 12 V, the number of cells in series are cells in series = 12 V/ (0.493 V/cell) = 24.3 cells - the number of cells in series can be rounding up to 25; two rows of 25 cells in parallel will required 50 cells with a total power of 126.5 W SOLUTION - the number of cells required for 120 W is number of cells = 120 W / (2.53 W/cell) = 47.2 cells - to provide the correct voltage 12 V, the number of cells in series are cells in series = 12 V/ (0.493 V/cell) = 24.3 cells - the number of cells in series can be rounding up to 25; two rows of 25 cells in parallel will required 50 cells with a total power of 126.5 W Photovoltaics Energy Systems Photovoltaics Energy Systems Stand Alone PV Systems with Battery Backup Renewable Energy Technologies How do we get “connected”? Photovoltaics Energy Systems Example: Building Integrated Solar Cells (Goodwin Hall @ Queen’s) Building Integrated Solar Cells: Construction Utility-Scale Grid-Connected PV Solar Generation in Ontario Large scale (transmission-level grid) solar expected to come into service in early 2014. A list of solar projects are scheduled to come in service by Winter 2015 Haldimand Solar Project (100 MW) 2014-Q1 Silvercreek Solar Park (10 MW) 2014-Q3 Liskeard 1 (10 MW) 2014-Q3 Liskeard 2 (10 MW) 2014-Q3 Liskeard 3 (10 MW) 2014-Q3 Northland Power Solar Abitibi (10 MW) 2014-Q3 Northland Power Solar Empire (10 MW) 2014-Q3 Northland Power Solar Long Lake (10 MW) 2014-Q3 Northland Power Solar Martin’s Meadows (10 MW) 2014-Q3 Kingston Solar Project (100 MW) 2014-Q4 https://www.ieso.ca/imoweb/marketdata/windpower.asp PV versus Solar Thermal Physics: Where Does the Energy Go? PV • • • • 10 – 15% Electricity 10% Optical loss 75 – 80 % Waste Heat $1 - $2 /Watt Thermal • • • • 15% Optical loss 45% Useful Heat 40% Heat Losses $1-3 /Watt (thermal) EcoTerraTM EQuilibrium House (Alouette Homes) – an example of transformative SBRN work 2.8-kW Buildingintegrated photovoltaicthermal system Passive solar design: Optimized triple glazed windows and mass Prefabricated home Partners: NRCan, CMHC designed to have close to net-zero annual energy consumption Groundsource heat pump Active Solar Thermal Energy Systems • Can generate “clean & green” energy - Photovoltaics >>> electrical energy - Solar Thermal >>> thermal energy • high capital cost - low fuel cost • Both can displace conventional energy and power production/consumption and reduce peak loads Residential Solar Heating Applications Solar Collection Basics: Collector Types • Stationary – Fixed racks or roof installation – No moving mechanical components – Radiation intensity varies over day and season • Tracking – Increases incident solar radiation – Enables high concentrations/temperatures – Usually increased mechanical complexity • Hybrids – “Fixed” racks can be adjusted in tilt to account for seasonal variations – Tracking collectors can be single or dual axis tracking Glazed Flat-Plate Collectors Advantages • offers multiple mounting options • good price/performance ratio • typically cheaper than vacuum collector • proven performance --durable Disadvantages • lower efficiency for high temperature applications because the heat loss coefficient is higher (recent work on multi-glazed is improving high temperature performance) • not normally used for generating high temperatures (+100oC) • may be heavier than other options Flat Plate Solar Collector Designs The task of a solar collector is to achieve the highest possible thermal yield. Different collector designs From “Planning and Installing Solar Thermal Systems”, James & James/Earthscan, London, UK Glazed Flat-Plate Collectors 1. Frame 2. Seal 3. Transparent cover 4. Frame – side-wall profile 5. Thermal insulation 6. Full-surface absorber 7. Fluid channel 8. Fixing slot 9. Rear wall From “Planning and Installing Solar Thermal Systems”, James & James/Earthscan, London, UK Unglazed Swimming Pool Collectors Evacuated Tube Collectors (ETC’s) Advantages • achieves a high efficiency even with large ΔT’s between absorber and surroundings • low in weight, can be assembled at installation site • may have lower wind loading? Disadvantages • more expensive than a glazed flat-plate collector • cannot be used for in-roof installation • most heat pipe systems need to be inclined at least 25o tilt to horizontal Typical Efficiencies of Collectors Solar Collector Performance Plots Ambient 0.9 0.8 Low Temp High Temp Medium 0.7 Efficiency 0.6 0.5 1 0.4 0.3 2 3 1 - Vacuum Tube Collector 0.2 0.1 3 - Unglazed Swimming Pool Absorber 2 - Glazed Flat Plate Collector 0 (Ti-Ta)/G, (m2 oC) / W Solar collector efficiencies generally fall within specific ranges. # FR ( )e FR UL (W/m2oC) 1 0.5 - 0.75 1-2 Depends on tube spacing for ETC 2 0.65 - 0.8 3-8 Depends on # of covers and absorber coating 3 0.8 - 0.95 10 - 20 Depends on wind speed Sun Tracking Concentrating Solar Collectors Concentration of solar radiation to increase high temperature performance Concentration of solar radiation: single reflector with two-axis tracking From “Planning and Installing Solar Thermal Systems”, James & James/Earthscan, London, UK Concentration of solar radiation: multiple reflectors with two-axis tracking Power Generation Systems Usually use high temperature concentrating collectors to produce steam to turn a turbine/generator unit.. Suitable for locations with clear sunny days Concentrating Solar Collectors Parabolic Trough Collectors The world's largest solar power facility, located near Kramer Junction, CA. Solar Air Preheat Source: http://www.rockymtsolar.com/ Source: http://oee.nrcan.gc.ca/ Solar Air Heating Systems Solar Water Heating Systems Types Thermosyphon bread box Close coupled Drain Down Drain Back Closed Loop anti-freeze Solar Domestic Hot Water (Passive Systems) Source: http://www.volker-quaschning.de/ From “Solar Thermal Systems”, James & James, London, UK Passive solar systems have no pumps, controls, or moving parts. Indirect Solar Domestic Hot Water System Solar Collector Fixed Flow Rate Roof Line Hot Water to Load Storage Tank Heat Exchanger Electric Pump Variable Flow Rate Storage Tank Cold Mains Inlet Solar Domestic Hot Water Heating 6.1. Howard Johnson Hotel in Kingston HOSPITAL FOR SICK CHILDREN, TORONTO Commercial Systems System Description: • Green Phoenix Apt Toronto Canada • 40 EnerWorks collectors • 93,798 kWh per year • 27% solar fraction • 4 year payback Example Projects Commercial Installations Toronto Hospital For Sick Children - 92 collectors offsets domestic hot water U of T 100 Collectors 6 x 454 L storage tanks System Schematic Drake Landing Solar District Heating Source: “http://www.dlsc.ca/” Drake’s Landing Solar Community Highlights • the largest subdivision of R-2000 single family homes in Canada, each 30% more efficient than conventionally built homes • a first in the world, 90% of residential space heating needs will be met by solar thermal energy. • a reduction of approximately 5 tonnes of greenhouse gas (GHG) emissions per home per year Drake Landing Solar Community (Okotoks Alberta) > 95% annual Solar Fraction for space and water heating District Heating System • there are four individual home-run loops off a manifold in the Energy Centre • plastic, insulated, underground pipe is used to distribute heated water from the community’s Energy Centre back to the homes Source: “http://www.dlsc.ca/” Thermal Storage and Demand Side Management The Energy Centre 87