Line+Inquiry+3+IMPORTANT+(4)

__ Line Inquiry 3 Info IMPORTANT 4 __  With the scarcity of flat land within an area of only 1097 square km accommodating a high and ever increasing population, we need enormous energy resources to create a habitable indoor environment inside the high-rise commercial and residential buildings. We also need a great deal of energy resources to light up our night sky, to sustain the intense human activities right into the mid-night. We also need a lot of energy resources to drive our infrastructure machinery - our water supply, drainage systems and road networks. Of course we need energy to provide mobility for everyone of us - railway, trams, cars, airplanes. However, there are no indigenous energy resources in Hong Kong, we have to rely totally on imported fuels, and we know that fossil fuels are already exhausting. To explain the energy scene of Hong Kong, we first look at two major aggregate energy indicators: the "Primary Energy Requirements" (the equivalent of "Total Primary Energy Supply (TPS)" of other economies) and the "Final Energy Requirements" (the equivalent of "Total Final Energy Consumption (TFC)" of other economies).  "Primary energy requirements" (PER) refers to the overall energy consumption within the geographic territory. It represents the total supply of energy available to the territory, which supports all the requirements for energy transformation and final consumption in that territory, and includes both indigenous energy sources and imported energy commodities consumed within the territory. In the case of Hong Kong, it is calculated from retained imports of coal and oil products net of bunkers' usage and exports of electricity, after adjustment for supply from stock.  "Final energy requirements" (FER) refers to the amount of energy consumed by final users for all energy purposes such as heating, cooking and driving machinery, but excludes non-energy usages such as using kerosene as solvent. It differs from PER in that the latter includes all energy used or lost in the energy transformation and the distribution process.  There are a number of crucial factors influencing the PER and FER trends:  (a) The Hong Kong economy has been changing very rapidly from an industry-driven economy to a services-driven economy. Industries embarked on a massive migration into the Mainland, starting in the 1980s and accelerated in the 1990s.  (b) The opening up of the Mainland markets on the other hand provided opportunities for our trading, financial, banking, insurance, and transport services. This led to large increase in energy consumption in the services sector. Besides, the increasing volume of trading activities through the Hong Kong ports also led to a large increase in transport energy consumption.  (c) On the supply side, there was a shift in electricity generation from coal-based to firstly imported nuclear and then to natural gas.  In the PER and FER trends, these effects offset each other to some extent. Moreover, the effect of the "swings" mentioned above further complicates the trends. Apart from PER and FER, we at the Energy Efficiency Office also compile the [|Hong Kong Energy End-use Database]. The Energy End-use Database provides the Government with energy information base and analytical tools for evaluating energy efficiency policies. We have also developed [|energy consumption indicators and benchmarks] for the commercial and transport sectors. A [|software tool] is also available for users to benchmark their energy consumption levels with others in Hong Kong. __ []  __  Applications of solar technology

 Average [|insolation] showing land area (small black dots) required to replace the world primary energy supply with solar electricity. 18 TW is 568 Exajoule (EJ) per year. Insolation for most people is from 150 to 300 W/m2 or 3.5 to 7.0 kWh/m2/day.   Solar energy refers primarily to the use of [|solar radiation] for practical ends. However, all renewable energies, other than [|geothermal] and [|tidal], derive their energy from the sun.  Solar technologies are broadly characterized as either passive or active depending on the way they capture, convert and distribute sunlight. Active solar techniques use photovoltaic panels, pumps, and fans to convert sunlight into useful outputs. Passive solar techniques include selecting materials with favorable thermal properties, designing spaces that naturally circulate air, and referencing the position of a building to the Sun. Active solar technologies increase the supply of energy and are considered [|supply side] technologies, while passive solar technologies reduce the need for alternate resources and are generally considered demand side technologies. [|[16] ] ** Architecture and urban planning ** // Main articles: [|Passive solar building design] and [|Urban heat island] //  [|Darmstadt University of Technology]  in [|Germany] won the 2007 [|Solar Decathlon] in [|Washington, D.C.] with this [|passive house] designed specifically for the humid and hot subtropical climate. [|[17] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Sunlight has influenced building design since the beginning of architectural history. [|[18] ] Advanced solar architecture and urban planning methods were first employed by the [|Greeks] and [|Chinese], who oriented their buildings toward the south to provide light and warmth. [|[19] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> The common features of [|passive solar] architecture are orientation relative to the Sun, compact proportion (a low surface area to volume ratio), selective shading (overhangs) and [|thermal mass]. [|[18] ] When these features are tailored to the local climate and environment they can produce well-lit spaces that stay in a comfortable temperature range. [|Socrates'] Megaron House is a classic example of passive solar design. [|[18] ] The most recent approaches to solar design use computer modeling tying together [|solar lighting], [|heating] and [|ventilation] systems in an integrated [|solar design] package. [|[20] ] [|Active solar] equipment such as pumps, fans and switchable windows can complement passive design and improve system performance. <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Urban heat islands (UHI) are metropolitan areas with higher temperatures than that of the surrounding environment. The higher temperatures are a result of increased absorption of the Solar light by urban materials such as asphalt and concrete, which have lower [|albedos] and higher [|heat capacities] than those in the natural environment. A straightforward method of counteracting the UHI effect is to paint buildings and roads white and plant trees. Using these methods, a hypothetical "cool communities" program in [|Los Angeles] has projected that urban temperatures could be reduced by approximately 3 °C at an estimated cost of US$1 billion, giving estimated total annual benefits of US$530 million from reduced air-conditioning costs and healthcare savings. [|[21] ] <span style="mso-layout-grid-align: none; mso-line-height-alt: 15.0pt; mso-pagination: none; text-autospace: none;">** Agriculture and horticulture **

<span style="mso-layout-grid-align: none; mso-line-height-alt: 15.0pt; mso-pagination: none; text-autospace: none;">  [|Greenhouses]  like these in the Westland municipality of the [|Netherlands] grow vegetables, fruits and flowers. <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> [|Agriculture] and [|horticulture] seek to optimize the capture of solar energy in order to optimize the productivity of plants. Techniques such as timed planting cycles, tailored row orientation, staggered heights between rows and the mixing of plant varieties can improve crop yields. [|[22] ] [|[23] ] While sunlight is generally considered a plentiful resource, the exceptions highlight the importance of solar energy to agriculture. During the short growing seasons of the [|Little Ice Age], French and [|English] farmers employed fruit walls to maximize the collection of solar energy. These walls acted as thermal masses and accelerated ripening by keeping plants warm. Early fruit walls were built perpendicular to the ground and facing south, but over time, sloping walls were developed to make better use of sunlight. In 1699, [|Nicolas Fatio de Duillier] even suggested using a [|tracking mechanism] which could pivot to follow the Sun. [|[24] ] Applications of solar energy in agriculture aside from growing crops include pumping water, drying crops, brooding chicks and drying chicken manure. [|[25] ] [|[26] ] More recently the technology has been embraced by vinters, who use the energy generated by solar panels to power grape presses. [|[27] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> [|Greenhouses] convert solar light to heat, enabling year-round production and the growth (in enclosed environments) of specialty crops and other plants not naturally suited to the local climate. Primitive greenhouses were first used during Roman times to produce [|cucumbers] year-round for the Roman emperor [|Tiberius]. [|[28] ] The first modern greenhouses were built in Europe in the 16th century to keep exotic plants brought back from explorations abroad. [|[29] ] Greenhouses remain an important part of horticulture today, and plastic transparent materials have also been used to similar effect in [|polytunnels] and [|row covers]. <span style="mso-layout-grid-align: none; mso-line-height-alt: 15.0pt; mso-pagination: none; text-autospace: none;">** Solar lighting ** <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Daylighting features such as this [|oculus] at the top of the [|Pantheon], in [|Rome] , Italy have been in use since antiquity. <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> The history of lighting is dominated by the use of natural light. The Romans recognized a [|right to light] as early as the [|6th century] and English law echoed these judgments with the Prescription Act of 1832. [|[30] ] [|[31] ] In the 20th century artificial [|lighting] became the main source of interior illumination but daylighting techniques and hybrid solar lighting solutions are ways to reduce energy consumption. <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> [|Daylighting] systems collect and distribute sunlight to provide interior illumination. This passive technology directly offsets energy use by replacing artificial lighting, and indirectly offsets non-solar energy use by reducing the need for [|air-conditioning]. [|[32] ] Although difficult to quantify, the use of [|natural lighting] also offers physiological and psychological benefits compared to [|artificial lighting]. [|[32] ] Daylighting design implies careful selection of window types, sizes and orientation; exterior shading devices may be considered as well. Individual features include sawtooth roofs, [|clerestory windows], light shelves, [|skylights] and [|light tubes]. They may be incorporated into existing structures, but are most effective when integrated into a [|solar design] package that accounts for factors such as [|glare], heat flux and [|time-of-use]. When daylighting features are properly implemented they can reduce lighting-related energy requirements by 25%. [|[33] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> [|Hybrid solar lighting] is an [|active solar] method of providing interior illumination. HSL systems collect sunlight using focusing mirrors that [|track the Sun] and use [|optical fibers] to transmit it inside the building to supplement conventional lighting. In single-story applications these systems are able to transmit 50% of the direct sunlight received. [|[34] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Solar lights that charge during the day and light up at dusk are a common sight along walkways.[[|//citation needed//]] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Although [|daylight saving time] is promoted as a way to use sunlight to save energy, recent research has been limited and reports contradictory results: several studies report savings, but just as many suggest no effect or even a net loss, particularly when [|gasoline] consumption is taken into account. Electricity use is greatly affected by geography, climate and economics, making it hard to generalize from single studies. [|[35] ] <span style="mso-layout-grid-align: none; mso-line-height-alt: 15.0pt; mso-pagination: none; text-autospace: none;">** Solar thermal ** <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;">// Main article: [|Solar thermal energy] // <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Solar thermal technologies can be used for water heating, space heating, space cooling and process heat generation. [|[36] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;">** Water heating ** <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;">// Main articles: [|Solar hot water] and [|Solar combisystem] // <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Solar water heaters facing the [|Sun] to maximize gain. <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Solar hot water systems use sunlight to heat water. In low geographical latitudes (below 40 degrees) from 60 to 70% of the domestic hot water use with temperatures up to 60 °C can be provided by solar heating systems. [|[37] ] The most common types of solar water heaters are evacuated tube collectors (44%) and glazed flat plate collectors (34%) generally used for domestic hot water; and unglazed plastic collectors (21%) used mainly to heat swimming pools. [|[38] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> As of 2007, the total installed capacity of solar hot water systems is approximately 154 [|GW]. [|[39] ] China is the world leader in their deployment with 70 GW installed as of 2006 and a long term goal of 210 GW by 2020. [|[40] ] Israel and [|Cyprus] are the per capita leaders in the use of solar hot water systems with over 90% of homes using them. [|[41] ] In the United States, Canada and Australia heating swimming pools is the dominant application of solar hot water with an installed capacity of 18 GW as of 2005. [|[16] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;">** Heating, cooling and ventilation ** <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;">// Main articles: [|Solar heating], [|Thermal mass] , [|Solar chimney] , and [|Solar air conditioning] // <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Solar House #1 of [|Massachusetts Institute of Technology] in the United States, built in 1939, used [|seasonal thermal storage] for year-round heating. <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> In the United States, [|heating, ventilation and air conditioning] (HVAC) systems account for 30% (4.65 EJ) of the energy used in commercial buildings and nearly 50% (10.1 EJ) of the energy used in residential buildings. [|[33] ] [|[42] ] Solar heating, cooling and ventilation technologies can be used to offset a portion of this energy. <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Thermal mass is any material that can be used to store heat—heat from the Sun in the case of solar energy. Common thermal mass materials include stone, cement and water. Historically they have been used in arid climates or warm temperate regions to keep buildings cool by absorbing solar energy during the day and radiating stored heat to the cooler atmosphere at night. However they can be used in cold temperate areas to maintain warmth as well. The size and placement of thermal mass depend on several factors such as climate, daylighting and shading conditions. When properly incorporated, thermal mass maintains space temperatures in a comfortable range and reduces the need for auxiliary heating and cooling equipment. [|[43] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> A solar chimney (or thermal chimney, in this context) is a passive solar ventilation system composed of a vertical shaft connecting the interior and exterior of a building. As the chimney warms, the air inside is heated causing an [|updraft] that pulls air through the building. Performance can be improved by using glazing and thermal mass materials in a way that mimics greenhouses.[[|//citation needed//]] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> [|Deciduous] trees and plants have been promoted as a means of controlling solar heating and cooling. When planted on the southern side of a building, their leaves provide shade during the summer, while the bare limbs allow light to pass during the winter. [|[44] ] Since bare, leafless trees shade 1/3 to 1/2 of incident solar radiation, there is a balance between the benefits of summer shading and the corresponding loss of winter heating. [|[45] ] In climates with significant heating loads, deciduous trees should not be planted on the southern side of a building because they will interfere with winter solar availability. They can, however, be used on the east and west sides to provide a degree of summer shading without appreciably affecting winter solar gain. [|[46] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;">** Water treatment ** <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;">// Main articles: [|Solar still], [|Solar water disinfection] , [|Solar desalination] , and [|Solar Powered Desalination Unit] // <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Solar water disinfection in [|Indonesia] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Small scale solar powered sewerage treatment plant. <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Solar distillation can be used to make [|saline] or [|brackish water] potable. The first recorded instance of this was by 16th century Arab alchemists. [|[47] ] A large-scale solar distillation project was first constructed in 1872 in the [|Chilean] mining town of Las Salinas. [|[48] ] The plant, which had solar collection area of 4,700 m2, could produce up to 22,700 [|L] per day and operated for 40 years. [|[48] ] Individual [|still] designs include single-slope, double-slope (or greenhouse type), vertical, conical, inverted absorber, multi-wick, and multiple effect. [|[47] ] These stills can operate in passive, active, or hybrid modes. Double-slope stills are the most economical for decentralized domestic purposes, while active multiple effect units are more suitable for large-scale applications. [|[47] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Solar water [|disinfection] (SODIS) involves exposing water-filled plastic [|polyethylene terephthalate] (PET) bottles to sunlight for several hours. [|[49] ] Exposure times vary depending on weather and climate from a minimum of six hours to two days during fully overcast conditions. [|[50] ] It is recommended by the [|World Health Organization] as a viable method for household water treatment and safe storage. [|[51] ] Over two million people in developing countries use this method for their daily drinking water. [|[50] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Solar energy may be used in a water stabilisation pond to treat [|waste water] without chemicals or electricity. A further environmental advantage is that [|algae] grow in such ponds and consume [|carbon dioxide] in photosynthesis, although algae may produce toxic chemicals that make the water unusable. [|[52] ] [|[53] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;">** Cooking ** <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;">// Main article: [|Solar cooker] // <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> The Solar Bowl in [|Auroville], [|India] , concentrates sunlight on a movable receiver to produce [|steam] for [|cooking]. <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Solar cookers use sunlight for cooking, drying and [|pasteurization]. They can be grouped into three broad categories: box cookers, panel cookers and reflector cookers. [|[54] ] The simplest solar cooker is the box cooker first built by [|Horace de Saussure] in 1767. [|[55] ] A basic box cooker consists of an insulated container with a transparent lid. It can be used effectively with partially overcast skies and will typically reach temperatures of 90–150 °C. [|[56] ] Panel cookers use a reflective panel to direct sunlight onto an insulated container and reach temperatures comparable to box cookers. Reflector cookers use various concentrating geometries (dish, trough, Fresnel mirrors) to focus light on a cooking container. These cookers reach temperatures of 315 °C and above but require direct light to function properly and must be repositioned to track the Sun. [|[57] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> The [|solar bowl] is a concentrating technology employed by the Solar Kitchen in [|Auroville], [|Pondicherry] , [|India] , where a stationary spherical reflector focuses light along a line perpendicular to the sphere's interior surface, and a computer control system moves the receiver to intersect this line. Steam is produced in the receiver at temperatures reaching 150 °C and then used for process heat in the kitchen. [|[58] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> A reflector developed by [|Wolfgang Scheffler] in 1986 is used in many solar kitchens. Scheffler reflectors are flexible parabolic dishes that combine aspects of trough and power tower concentrators. [|Polar tracking] is used to follow the Sun's daily course and the curvature of the reflector is adjusted for seasonal variations in the incident angle of sunlight. These reflectors can reach temperatures of 450–650 °C and have a fixed focal point, which simplifies cooking. [|[59] ] The world's largest Scheffler reflector system in Abu Road, [|Rajasthan], India is capable of cooking up to 35,000 meals a day. [|[60] ] As of 2008, over 2,000 large Scheffler cookers had been built worldwide. [|[61] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;">** Process heat ** <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;">// Main articles: [|Solar pond], [|Salt evaporation pond] , and [|Solar furnace] // <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> STEP parabolic dishes used for steam production and electrical generation. <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Solar concentrating technologies such as parabolic dish, trough and Scheffler reflectors can provide process heat for commercial and industrial applications. The first commercial system was the [|Solar Total Energy Project] (STEP) in Shenandoah, Georgia, USA where a field of 114 parabolic dishes provided 50% of the process heating, air conditioning and electrical requirements for a clothing factory. This grid-connected cogeneration system provided 400 kW of electricity plus thermal energy in the form of 401 kW steam and 468 kW chilled water, and had a one hour peak load thermal storage. [|[62] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Evaporation ponds are shallow pools that concentrate dissolved solids through [|evaporation]. The use of evaporation ponds to obtain salt from sea water is one of the oldest applications of solar energy. Modern uses include concentrating brine solutions used in leach mining and removing dissolved solids from waste streams. [|[63] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> [|Clothes lines], [|clotheshorses] , and clothes racks dry clothes through evaporation by wind and sunlight without consuming electricity or gas. In some states of the United States legislation protects the "right to dry" clothes. [|[64] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Unglazed transpired collectors (UTC) are perforated sun-facing walls used for preheating ventilation air. UTCs can raise the incoming air temperature up to 22 °C and deliver outlet temperatures of 45–60 °C. [|[65] ] The short payback period of transpired collectors (3 to 12 years) makes them a more cost-effective alternative than glazed collection systems. [|[65] ] As of 2003, over 80 systems with a combined collector area of 35,000 [|m2] had been installed worldwide, including an 860 m2 collector in [|Costa Rica] used for drying coffee beans and a 1,300 m2 collector in [|Coimbatore], India used for drying marigolds. [|[26] ] <span style="mso-layout-grid-align: none; mso-line-height-alt: 15.0pt; mso-pagination: none; text-autospace: none;">** Electrical generation ** <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;">// Main article: [|Solar power] // <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> The [|PS10] concentrates sunlight from a field of heliostats on a central tower. <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Solar power is the conversion of sunlight into [|electricity], either directly using [|photovoltaics] (PV), or indirectly using [|concentrated solar power] (CSP). CSP systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. PV converts light into electric current using the [|photoelectric effect]. <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Commercial CSP plants were first developed in the 1980s, and the 354 MW [|SEGS] CSP installation is the largest solar power plant in the world and is located in the Mojave Desert of California. Other large CSP plants include the [|Solnova Solar Power Station] (150 MW) and the [|Andasol solar power station] (100 MW), both in Spain. The 80 MW [|Sarnia Photovoltaic Power Plant] in [|Canada], is the [|world’s largest] [|photovoltaic plant]. <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;">** Experimental solar power ** <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;">// Main articles: [|Solar pond] and [|Thermogenerator] // <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Solar Evaporation Ponds in the [|Atacama Desert], South America <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> A [|solar pond] is a pool of salt water (usually 1–2 [|m] deep) that collects and stores solar energy. Solar ponds were first proposed by Dr. Rudolph Bloch in 1948 after he came across reports of a lake in [|Hungary] in which the temperature increased with depth. This effect was due to salts in the lake's water, which created a "density gradient" that prevented [|convection currents]. A prototype was constructed in 1958 on the shores of the Dead Sea near [|Jerusalem]. [|[66] ] The pond consisted of layers of water that successively increased from a weak salt solution at the top to a [|high salt] solution at the bottom. This solar pond was capable of producing temperatures of 90 °C in its bottom layer and had an estimated solar-to-electric efficiency of two percent. <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> [|Thermoelectric], or "thermovoltaic" devices convert a temperature difference between dissimilar materials into an electric current. First proposed as a method to store solar energy by solar pioneer Mouchout in the 1800s, [|[67] ] thermoelectrics reemerged in the Soviet Union during the 1930s. Under the direction of Soviet scientist [|Abram Ioffe] a concentrating system was used to thermoelectrically generate power for a 1 [|hp] engine. [|[68] ] Thermogenerators were later used in the US space program as an energy conversion technology for powering deep space missions such as [|Cassini], [|Galileo] and [|Viking]. Research in this area is focused on raising the efficiency of these devices from 7–8% to 15–20%. [|[69] ] <span style="mso-layout-grid-align: none; mso-line-height-alt: 15.0pt; mso-pagination: none; text-autospace: none;">** Solar chemical ** <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;">// Main article: [|Solar chemical] // <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Solar chemical processes use solar energy to drive chemical reactions. These processes offset energy that would otherwise come from an alternate source and can convert solar energy into storable and transportable fuels. Solar induced chemical reactions can be divided into thermochemical or [|photochemical]. [|[70] ] A variety of fuels can be produced by [|artificial photosynthesis]. [|[71] ] The multielectron catalytic chemistry involved in making carbon-based fuels (such as [|methanol] ) from reduction of [|carbon dioxide] is challenging; a feasible alternative is [|hydrogen] production from protons, though use of water as the source of electrons (as plants do) requires mastering the multielectron oxidation of two water molecules to molecular oxygen. [|[72] ] Some have envisaged working solar fuel plants in coastal metropolitan areas by 2050- the splitting of sea water providing hydrogen to be run through adjacent fuel-cell electric power plants and the pure water by-product going directly into the municipal water system. [|[73] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> [|Hydrogen production] technologies been a significant area of solar chemical research since the 1970s. Aside from electrolysis driven by photovoltaic or photochemical cells, several thermochemical processes have also been explored. One such route uses concentrators to split water into oxygen and hydrogen at high temperatures (2300-2600 °C). [|[74] ] Another approach uses the heat from solar concentrators to drive the [|steam reformation] of natural gas thereby increasing the overall hydrogen yield compared to conventional reforming methods. [|[75] ] Thermochemical cycles characterized by the decomposition and regeneration of reactants present another avenue for hydrogen production. The Solzinc process under development at the [|Weizmann Institute] uses a 1 MW solar furnace to decompose [|zinc oxide] (ZnO) at temperatures above 1200 °C. This initial reaction produces pure zinc, which can subsequently be reacted with water to produce hydrogen. [|[76] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> [|Sandia's] Sunshine to Petrol (S2P) technology uses the high temperatures generated by concentrating sunlight along with a [|zirconia] / [|ferrite] catalyst to break down atmospheric carbon dioxide into oxygen and [|carbon monoxide] (CO). The carbon monoxide can then be used to synthesize conventional fuels such as methanol, gasoline and jet fuel. [|[77] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> A photogalvanic device is a type of battery in which the cell solution (or equivalent) forms energy-rich chemical intermediates when illuminated. These energy-rich intermediates can potentially be stored and subsequently reacted at the electrodes to produce an electric potential. The ferric-thionine chemical cell is an example of this technology. [|[78] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Photoelectrochemical cells or PECs consist of a semiconductor, typically titanium dioxide or related titanates, immersed in an electrolyte. When the semiconductor is illuminated an electrical potential develops. There are two types of photoelectrochemical cells: photoelectric cells that convert light into electricity and photochemical cells that use light to drive chemical reactions such as [|electrolysis]. [|[79] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> A combination thermal/photochemical cell has also been proposed. The Stanford PETE process uses solar thermal energy to raise the temperature of a thermionic metal to about 800C to increase the rate of production of electricity to electrolyse atmospheric CO2 down to carbon or carbon monoxide which can then be used for fuel production, and the waste heat can be used as well. [|[80] ] <span style="mso-layout-grid-align: none; mso-line-height-alt: 15.0pt; mso-pagination: none; text-autospace: none;">** Solar vehicles ** <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;">// Main articles: [|Solar vehicle], [|Solar-charged vehicle] , [|Electric boat] , and [|Solar balloon] // <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Australia hosts the [|World Solar Challenge] where solar cars like the Nuna3 race through a 3,021 km (1,877 mi) course from Darwin to Adelaide. <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Development of a solar powered car has been an engineering goal since the 1980s. The [|World Solar Challenge] is a biannual solar-powered car race, where teams from universities and enterprises compete over 3,021 kilometres (1,877 mi) across central Australia from [|Darwin] to [|Adelaide]. In 1987, when it was founded, the winner's average speed was 67 kilometres per hour (42 mph) and by 2007 the winner's average speed had improved to 90.87 kilometres per hour (56.46 mph). [|[81] ] The [|North American Solar Challenge] and the planned [|South African Solar Challenge] are comparable competitions that reflect an international interest in the engineering and development of solar powered vehicles. [|[82] ] [|[83] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Some vehicles use solar panels for auxiliary power, such as for air conditioning, to keep the interior cool, thus reducing fuel consumption. [|[84] ] [|[85] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> In 1975, the first practical solar boat was constructed in England. [|[86] ] By 1995, passenger boats incorporating PV panels began appearing and are now used extensively. [|[87] ] In 1996, [|Kenichi Horie] made the first solar powered crossing of the Pacific Ocean, and the //sun21// catamaran made the first solar powered crossing of the Atlantic Ocean in the winter of 2006–2007. [|[88] ] There are plans to circumnavigate the globe in 2010. [|[89] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> Helios UAV in solar powered flight. <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> In 1974, the unmanned [|AstroFlight Sunrise] plane made the first solar flight. On 29 April 1979, the[|//Solar Riser//] made the first flight in a solar powered, fully controlled, man carrying flying machine, reaching an altitude of 40 feet (12 m). In 1980, the [|//Gossamer Penguin//] made the first piloted flights powered solely by photovoltaics. This was quickly followed by the [|//Solar Challenger//] which crossed the English Channel in July 1981. In 1990 [|Eric Scott Raymond] in 21 hops flew from California to North Carolina using solar power. [|[90] ] Developments then turned back to unmanned aerial vehicles (UAV) with the [|//Pathfinder//] (1997) and subsequent designs, culminating in the [|//Helios//] which set the altitude record for a non-rocket-propelled aircraft at 29,524 metres (96,864 ft) in 2001. [|[91] ] The[|//Zephyr//], developed by [|BAE Systems], is the latest in a line of record-breaking solar aircraft, making a 54-hour flight in 2007, and month-long flights are envisioned by 2010. [|[92] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> A [|solar balloon] is a black balloon that is filled with ordinary air. As sunlight shines on the balloon, the air inside is heated and expands causing an upward [|buoyancy] force, much like an artificially heated [|hot air balloon]. Some solar balloons are large enough for human flight, but usage is generally limited to the toy market as the surface-area to payload-weight ratio is relatively high. [|[93] ] <span style="line-height: 15.0pt; mso-layout-grid-align: none; mso-pagination: none; text-autospace: none;"> [|Solar sails] are a proposed form of spacecraft propulsion using large [|membrane mirrors] to exploit radiation pressure from the Sun. Unlike rockets, solar sails require no fuel. Although the thrust is small compared to rockets, it continues as long as the Sun shines onto the deployed sail and in the vacuum of space significant speeds can eventually be achieved. [|[94] ] The [|High-altitude airship] (HAA) is an unmanned, long-duration, lighter-than-air vehicle using [|helium] gas for lift, and [|thin film] solar cells for power. The [|United States Department of Defense] Missile Defense Agency has contracted [|Lockheed Martin] to construct it to enhance the [|Ballistic Missile Defense System] (BMDS). [|[95] ] Airships have some advantages for solar-powered flight: they do not require power to remain aloft, and an airship's envelope presents a large area to the Sun. __ []  __