What is Solar Energy? 1st LAW OF THERMODYNAMICS: Energy can be neither created nor destroyed, but only transformed. Solar Energy Example: You have electricity available at your house. If you plug a lamp into an receptacle, the energy is converted from electricity to light and heat. We convert energy from a variety of forms into forms we can more easily use. So….What Is Solar Energy? SOLAR ENERGY is energy from the sun that is converted into thermal or electrical energy. Solar Thermal What is THERMAL? THERMAL refers to HEAT Some similar words: Thermos Thermometer Therm(s): A measurement of heat, often associated with natural gas. British Thermal Units (BTU’s): The amount of heat needed to raise one pound of water one degree Fahrenheit. SOLAR THERMAL, in this context, is the practice of using the sun’s energy to produce heat, typically applied to water or other liquids. History: Solar Thermal This is the first practical application of solar thermal. It is basically a series of wooden boxes with glass tops known as a ‘hot box.’ Any idea when it was built? History: Solar Thermal The first practical application of solar thermal in Western history was built by a Swiss inventor, Horace de Saussure, in 1767. It was an insulated box with a glass top and two smaller boxes inside. When exposed to the sun, the bottom box heated to 228 degrees Fahrenheit. This has been the prototype for millions of solar water heaters, even many being built today. History: Solar Thermal A steam engine was invented in 1861 that was powered entirely by the sun. Also in the 19th century, European scientists developed collectors that could boil ammonia to perform work such as locomotion and refrigeration. The parabolic trough collector was also developed in the 19th century. The same basic design is still used today. History: Solar Thermal During the 19th century, in areas of the nation w/ few natural resources, many industrious Americans used large metal tanks to heat water by using energy from the sun. History: Solar Thermal History: Solar Thermal The first solar thermal system was patented in 1891 by a man named Clarence Kemp. History: Solar Thermal By 1897 one third of the homes in Pasadena, CA had water heated by solar thermal systems. By 1918 another manufacturer had sold over 4,000 solar water heaters. By 1941, over half the homes in Florida had solar water heaters. History: Solar Thermal Q: Are at least a third of Pasadena’s homes still using solar to heat their water? Q: Are at least half of Florida’s homes still using solar thermal? Q: Why or why not? History: Solar Thermal Q: What ultimately drives the solar thermal industry? History: Solar Thermal Q: What ultimately drives the solar thermal industry? A: Money When solar costs more than other energy sources, solar goes away. History: Solar Thermal The discovery of natural gas in California in the 1920’s drew an abrupt halt to the local solar thermal industry. After WWII, electricity rates dropped and stopped the solar thermal industry in Florida. History: Solar Thermal Japan doesn’t have an abundant source of coal, natural gas, or oil, so the cost of these energy sources encourages them to look elsewhere (to solar). In 1969 there were 4 million solar water heating tanks on Japanese homes. Today there are over 10 million solar thermal systems being used. Solar thermal is used on 90% of homes in Israel. Concentrating Solar Power (CSP) There are many kinds of high-temperature commercial solar thermal systems. These systems take solar heat and use it to make electricity. Parabolic Trough Power Tower Dish Designs Fresnel Reflectors Fresnel Lens Parabolic Trough Parabolic Trough Parabolic Trough Parabolic Trough Parabolic Trough The parabolic trough was developed in the late 1800s and patented in 1907. Parabolic Trough power plants use a curved trough which reflects the direct solar radiation onto a pipe containing a fluid (also called a receiver, absorber or collector) running the length of the trough, above the reflectors. These troughs track the sun on a single axis, from east to west. Parabolic Trough The receiver may be enclosed in a glass vacuum chamber. The vacuum significantly reduces convective heat loss. A fluid (also called heat transfer fluid) passes through the receiver and becomes very hot (around 400 degrees F). Common fluids are synthetic oil, molten salt and pressurized steam. The fluid containing the heat is transported to a heat engine where about a third of the heat is converted to electricity. Parabolic Trough Parabolic Trough The world’s largest parabolic trough facility is in the Mojave Desert near Barstow and consists of nine plants for a total of 354 megawatts of peak output. The individual plants range from 14 to 80 megawatts of capacity. Parabolic Trough Power Tower Power Tower Power Tower Power Towers (also known as 'central tower' power plants or 'heliostat' power plants) use an array of flat, moveable mirrors (called heliostats) to focus the sun's rays upon a collector tower (the receiver). Power Tower Power Tower The advantage of this design above the parabolic trough design is the higher temperature. Thermal energy at higher temperatures can be converted to electricity more efficiently and can be more cheaply stored for later use. The disadvantage is that each mirror must have its own dual-axis control, while in the parabolic trough design one axis can be shared for a large array of mirrors. Power Tower Power Tower The world's largest solar power tower plant is in Seville in Spain and is made up of more than 1200 mirrored heliostats surrounding a huge 54 story tower. This plant generates 20 megawatts of electricity, which is enough to supply 10,000 homes. Power Tower Power Tower Dish Designs Dish Designs A dish system uses a large, reflective, parabolic dish (shaped like a satellite television dish). It focuses all the sunlight that strikes the dish up onto to a single point above the dish, where a receiver captures the heat and transforms it into a useful form. Typically the dish is coupled with a Stirling engine in a Dish-Stirling System. From there the energy is converted into electricity. Dish Design The advantage of a dish system is that it can achieve much higher temperatures because of the higher concentration of light (like the tower designs). Higher temperatures leads to better conversion to electricity. Dish Design There are two main disadvantages: Heat to electricity conversion requires moving parts and that results in maintenance. The heavy engine is part of the moving structure, which requires a rigid frame and strong tracking system, which adds to the cost. Fresnel Reflector Fresnel Reflectors A linear Fresnel reflector power plant uses a series of long, narrow, shallow-curvature (or flat) mirrors to focus light onto one or more linear receivers positioned above the mirrors. On top of the receiver a small parabolic mirror can be attached for further focusing the light. Fresnel Reflector Fresnel Reflector Fresnel Lens Fresnel Lens The main advantage to this application is that these lenses cost less than mirrors. Solar Thermal Question: What do you do when the sun doesn’t shine? Heat Retention Storage of heat is possible with solar thermal. Steam accumulator: condenses/pressurizes steam and maintains heat. Only one hour of storage currently available with this method. Molten salts: store energy up to one week in cold storage tanks. Graphite: newer option. Not a lot of info available on storage characteristics, yet. Low Temp Solar Thermal Residential Water Heating: used for consumption, cooking, bathing, recreation (hot tub, swimming pool), space heating and cooling (radiant floor systems, ducted systems), etc. These systems collect or absorb the sun’s light, which is then turned into heat, and that heat directly or indirectly heats water. Low Temp Solar Thermal System Low Temp Solar Thermal Flat Plate Solar Thermal Collectors Flat Plate Collector The flat plate collector is the most common type of solar thermal collector. They use the basic concept Horace de Saussurre developed in 1767. Flat plate collectors do well in almost any environment and climate. Can heat water to 160 or 180 degrees Fahrenheit. Flat Plate Collector Evacuated Tube Collectors Evacuated Tube Collectors Evacuated Tube System Evacuated Tube System The vacuum in evacuated tubes helps reduce heat loss. Evacuated tubes have an ability to heat water to higher temperatures than other types of collectors, though over time a flat plate collector will typically produce more hot water between 140 and 180 degrees F. Evacuated tubes are only needed when water must be heated above 180 degrees F. Evacuated Tube Collectors Batch Heater Batch Heater Batch Heater Batch heaters work on the thermo-siphon principle. As water is heated in the collector it rises to the top and is channeled into the holding tank. Cooler water moves into the bottom of the collector to take its place, which continues the cycle. Batch heaters can be susceptible to heat loss at night, reducing financial and energy gains. Unglazed Polymer Collector Unglazed Collectors Unglazed collectors are commonly used for solar pool heating, but have recently been applied to domestic hot water systems. They are made of a polymer (a type of plastic) and are fairly inexpensive. They work best in Mediterranean climates and contribute heated water in the warm/hot summer months. They don’t do well in cold or windy environments. Unglazed Collector Unglazed Collector Solar Pool Heating Solar pool heating can be done with flat plate collectors, evacuated tubes, and unglazed collectors. Evacuated tube and flat plate collectors can’t have chlorine in them, so a heat exchanger must be used. Chlorinated water can run directly through unglazed collectors, making them more efficient at heating water in specific temperature ranges. Solar Pool Heating Solar Thermal - Commercial Solar Thermal - Commercial Commercial & Industrial: Used in Restaurants, Laundromats, heated aquatic centers, hotels, apartment complexes, manufacturing facilities, etc. Solar Thermal - Commercial Solar Thermal - Commercial Solar Thermal - Commercial Solar Thermal - Commercial Solar Thermal Passive Solar Passive Solar Q: What is Passive Solar? Passive Solar Q: What is Passive Solar? A: Passive Solar technologies use sunlight for useful energy without use of active mechanical systems (like pumps, motors, tracking units, etc). These technologies convert sunlight into usable heat (water, air, thermal mass), cause air- movement for ventilating, or future use, with little use of other energy sources. Solar History Greeks and Romans used passive solar designs to heat many of their homes and buildings in the cooler months by facing an opening or window to the south. The Greek city of Priene is illustrated here. Passive Solar Passive solar technologies include direct and indirect solar gain for space heating, solar water heating systems based on the thermosiphon, use of thermal mass and phase-change materials for slowing indoor air temperature swings, solar cookers, the solar chimney for enhancing natural ventilation, and earth sheltering. Passive Solar Trombe Wall Trombe Wall Solar Cooker Earth Sheltering Passive Solar Photovoltaics Q: What are Photovoltaics (PV)? Photovoltaics Q: What are Photovoltaics? A: Photovoltaics is a field of technology that uses solar cells to convert sunlight directly into electricity. PV System (Grid-Tied) PV System (Off-Grid) PV – Standalone PV - Standalone PV Components - Modules Module Composition Typical Cell Efficiencies Monocrystalline cells = 14-20% efficient Poly or multi crystalline cells = 10-12% efficient Thin Film Photovoltaics = roughly 6% efficient Mono Silicon Solar Module Mono Silicon Solar Module Solar Cell Poly or Multi Silicon Module Poly Silicon Cell Poly or Multi Silicon Module Thin Film PV Modules Thin Film Solar Thin Film Solar PV Components - Inverters PV Components - Inverters PV Components - Inverters PV Components - Inverters PV Components - Inverters PV Components - Inverters PV Components - Inverters Generator Questions?