sentence-transformers/squad huggingface dataset:
Passage: The Earth receives 174,000 terawatts (TW) of incoming solar radiation (insolation) at the upper atmosphere. Approximately 30% is reflected back to space while the rest is absorbed by clouds, oceans and land masses. The spectrum of solar light at the Earth's surface is mostly spread across the visible and near-infrared ranges with a small part in the near-ultraviolet. Most people around the world live in areas with insolation levels of 150 to 300 watts per square meter or 3.5 to 7.0 kWh/m2 per day.

Question: How many terawatts of solar radiation does the Earth receive?

Question: What percentage of solar radiation is reflected back by the atmosphere?

Question: The areas that people live in typically receive what range of kWh/m2 per day?

Question: How many terrawatts of radiation does the earth receive?

Question: How much of the solar radiation is reflected back into space?

Question: What are the insolation levels of most populated areas?

Question: Where is the solar radiation not reflected back to space absorbed?
Passage: Solar radiation is absorbed by the Earth's land surface, oceans – which cover about 71% of the globe – and atmosphere. Warm air containing evaporated water from the oceans rises, causing atmospheric circulation or convection. When the air reaches a high altitude, where the temperature is low, water vapor condenses into clouds, which rain onto the Earth's surface, completing the water cycle. The latent heat of water condensation amplifies convection, producing atmospheric phenomena such as wind, cyclones and anti-cyclones. Sunlight absorbed by the oceans and land masses keeps the surface at an average temperature of 14 °C. By photosynthesis green plants convert solar energy into chemically stored energy, which produces food, wood and the biomass from which fossil fuels are derived.

Question: The Earth's oceans cover what percentage of the globe?

Question: What is the average temperature of the Earth's surface in Celsius?

Question: What is the process by which green plants convert solar energy to stored energy?

Question: How much of the earth is covered by oceans?

Question: What is the cause of atmospheric circulation?

Question: How does the water vapor that rises in warm air turn into clouds?

Question: What creates wind, cyclones and anti-cyclones?

Question: What is the process in which plants convert solar energy into stored energy called?
Passage: The total solar energy absorbed by Earth's atmosphere, oceans and land masses is approximately 3,850,000 exajoules (EJ) per year. In 2002, this was more energy in one hour than the world used in one year. Photosynthesis captures approximately 3,000 EJ per year in biomass. The amount of solar energy reaching the surface of the planet is so vast that in one year it is about twice as much as will ever be obtained from all of the Earth's non-renewable resources of coal, oil, natural gas, and mined uranium combined,

Question: Each year the Earth absorbs how much solar energy in exajoules?

Question: In 2002, the Sun provided more energy in one hour than humans used in what span of time?

Question: How much energy in exajoules does photosynthesis capture each year?

Question: Twice the amount of energy obtainable by all the non-renewable sources on Earth can be provided by the Sun in what span of time?

Question: What is the amount of solar energy absorbed by the earth?

Question: How much solar energy is captured by photosynthesis?

Question: The amount of solar energy per year is twice as much as the energy that will ever be produced from what resources?
Passage: Solar technologies are broadly characterized as either passive or active depending on the way they capture, convert and distribute sunlight and enable solar energy to be harnessed at different levels around the world, mostly depending on distance from the equator. Although solar energy refers primarily to the use of solar radiation for practical ends, all renewable energies, other than geothermal and tidal, derive their energy from the Sun in a direct or indirect way.

Question: Where do the majority of renewable energies derive their energy from?

Question: How are solar technologies defined?

Question: What is one way that characterizes solar technologies as passive or active?

Question: Which renewable energies do not acquire their energy from the sun?

Question: How do renewable energies acquire energy from the sun?
Passage: Active solar techniques use photovoltaics, concentrated solar power, solar thermal collectors, 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.

Question: Are supply side solar technologies generally active or passive?

Question: Are demand side solar technologies generally active or passive?

Question: What is an active solar technique used to generate energy?

Question: What is an active solar technique used to generate energy?

Question: What does an active solar technique do?

Question: What does a passive solar technique do?
Passage: In 1897, Frank Shuman, a U.S. inventor, engineer and solar energy pioneer built a small demonstration solar engine that worked by reflecting solar energy onto square boxes filled with ether, which has a lower boiling point than water, and were fitted internally with black pipes which in turn powered a steam engine. In 1908 Shuman formed the Sun Power Company with the intent of building larger solar power plants. He, along with his technical advisor A.S.E. Ackermann and British physicist Sir Charles Vernon Boys, developed an improved system using mirrors to reflect solar energy upon collector boxes, increasing heating capacity to the extent that water could now be used instead of ether. Shuman then constructed a full-scale steam engine powered by low-pressure water, enabling him to patent the entire solar engine system by 1912.

Question: What was the name of the inventor who built a solar engine in 1897?

Question: In what year was the Sun Power Company formed?

Question: Shuman patented his solar engine system in what year?

Question: Who is Frank Shuman?

Question: In what year did solar engine build his solar engine?

Question: What was the solar engine used to power?

Question: In what year was the Sun Power Company established?

Question: In what year did Frank Shuman patent his solar engine?
Passage: Shuman built the world’s first solar thermal power station in Maadi, Egypt, between 1912 and 1913. Shuman’s plant used parabolic troughs to power a 45–52 kilowatts (60–70 hp) engine that pumped more than 22,000 litres (4,800 imp gal; 5,800 US gal) of water per minute from the Nile River to adjacent cotton fields. Although the outbreak of World War I and the discovery of cheap oil in the 1930s discouraged the advancement of solar energy, Shuman’s vision and basic design were resurrected in the 1970s with a new wave of interest in solar thermal energy. In 1916 Shuman was quoted in the media advocating solar energy's utilization, saying:

Question: Where did Shuman build the world's first solar thermal power station?

Question: How many liters of water per minute did Shuman's engine pump in litres?

Question: In what decade were Shuman's ideas about solar energy revived?

Question: Where was the first solar thermal power plant built?

Question: What was used to power the plants engine?

Question: From what river did the engine pump water?

Question: What slowed down the growth of solar energy?

Question: When was the interest in solar energy restored?
Passage: 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. 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.

Question: According to Shuman, up to what percentage of domestic hot water can be provided by solar heating systems?

Question: What do Solar hot water systems use to heat water?

Question: How much hot water can be produced by solar heating systems in low geographical latitudes?

Question: What is a common type of solar water heater?

Question: What type of solar water heater is used to heat pools?
Passage: As of 2007, the total installed capacity of solar hot water systems is approximately 154 thermal gigawatt (GWth). China is the world leader in their deployment with 70 GWth installed as of 2006 and a long-term goal of 210 GWth by 2020. Israel and Cyprus are the per capita leaders in the use of solar hot water systems with over 90% of homes using them. In the United States, Canada and Australia heating swimming pools is the dominant application of solar hot water with an installed capacity of 18 GWth as of 2005.

Question: What was the total capacity of solar hot water systems in 2007 in gigawatts?

Question: Over 90% of homes use solar hot water systems in which two countries?

Question: What is the capacity of a solar hot water system?

Question: What country is the leader in the implementation of solar powered hot water systems?

Question: What percentage of households use solar hot water systems in Israel and Cyprus?

Question: In what countries is the use to solar hot water used mainly for w=swimming pools?
Passage: In the United States, heating, ventilation and air conditioning (HVAC) systems account for 30% (4.65 EJ/yr) of the energy used in commercial buildings and nearly 50% (10.1 EJ/yr) of the energy used in residential buildings. Solar heating, cooling and ventilation technologies can be used to offset a portion of this energy.

Question: What percentage of energy in commercial buildings comes from HVAC systems?

Question: How much energy does an HVAC system use in commercial locations?

Question: How much energy does an HVAC system use in residential locations?

Question: What can be used to balance out a portion of the energy used by HVAC systems?
Passage: 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.

Question: Materials that can be used to store heat are known as what kind of mass?

Question: What is thermal mass?

Question: What are typical thermal mass material?

Question: How is thermal mass used to keep buildings cool?

Question: What is a something that determines the size of thermal mass?

Question: What does thermal mass reduce the need for?
Passage: 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.

Question: What kind of system is a solar chimney?

Question: What is a solar chimney?

Question: What is a solar chimney made of?

Question: How can the performance of a solar chimney be improved?
Passage: 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 in the northern hemisphere or the northern side in the southern hemisphere, their leaves provide shade during the summer, while the bare limbs allow light to pass during the winter. 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. In climates with significant heating loads, deciduous trees should not be planted on the Equator facing 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.

Question: The placement of deciduous trees on the Equator facing side of a building can have a negative effect on solar availability in which season?

Question: What is something that is used to control solar heating and cooling?

Question: How much solar radiation is blocked by leafless trees?

Question: Why should trees not be planted on the side of a building facing the equator?

Question: What side of a building should trees be planted without greatly affecting solar gain in the winter?
Passage: Solar cookers use sunlight for cooking, drying and pasteurization. They can be grouped into three broad categories: box cookers, panel cookers and reflector cookers. The simplest solar cooker is the box cooker first built by Horace de Saussure in 1767. 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 (194–302 °F). 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 (599 °F) and above but require direct light to function properly and must be repositioned to track the Sun.

Question: Horace de Saussure built the first box cooker in what year?

Question: Reflector cookers can reach temperatures in Celsius of up to what?

Question: What are solar cookers used for?

Question: What are the 3 main categories of solar cookers?

Question: Who created the box cooker?

Question: What is the typical temperature range for a box cooker?

Question: What do reflector cookers require to function?
Passage: 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. 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. 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. 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 (40 °F) and deliver outlet temperatures of 45–60 °C (113–140 °F). The short payback period of transpired collectors (3 to 12 years) makes them a more cost-effective alternative than glazed collection systems. As of 2003, over 80 systems with a combined collector area of 35,000 square metres (380,000 sq ft) had been installed worldwide, including an 860 m2 (9,300 sq ft) collector in Costa Rica used for drying coffee beans and a 1,300 m2 (14,000 sq ft) collector in Coimbatore, India, used for drying marigolds.

Question: The Solar Total Energy Project had a field of how many parabolic dishes?

Question: Are transpired collectors more or less cost-effective than glazed collection systems?

Question: What are some examples of solar concentrating technologies?

Question: What was the first commercial solar concentrating system?

Question: What is one of the oldest uses of solar energy?

Question: What are some items used to dry clothes without the use of electricity?

Question: What are Unglazed transpired collectors?
Passage: Solar distillation can be used to make saline or brackish water potable. The first recorded instance of this was by 16th-century Arab alchemists. A large-scale solar distillation project was first constructed in 1872 in the Chilean mining town of Las Salinas. The plant, which had solar collection area of 4,700 m2 (51,000 sq ft), could produce up to 22,700 L (5,000 imp gal; 6,000 US gal) per day and operate for 40 years. Individual still designs include single-slope, double-slope (or greenhouse type), vertical, conical, inverted absorber, multi-wick, and multiple effect. 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.

Question: In what year was a large scale solar distillation project constructed in Las Salinas?

Question: What is used to make saline or brackish water drinkable?

Question: By who was the first record of solar distillation done by?

Question: When was the first large solar distillation plant created?

Question: How much water was produced by the plant?

Question: What is an example of a solar distillation design?
Passage: Solar water disinfection (SODIS) involves exposing water-filled plastic polyethylene terephthalate (PET) bottles to sunlight for several hours. Exposure times vary depending on weather and climate from a minimum of six hours to two days during fully overcast conditions. It is recommended by the World Health Organization as a viable method for household water treatment and safe storage. Over two million people in developing countries use this method for their daily drinking water.

Question: Solar water disinfection is recommended by which organization?

Question: How long should the plastic bottles filled with water be exposed to sunlight during Solar water disinfection?

Question: What does the World Health Organization say about Solar water disinfection?

Question: How many people use Solar water disinfection to disinfect their drinking water?
Passage: 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.

Question: What is a possible negative effect of algae in water stabilization ponds?

Question: For what reason would solar energy be used in a water stabilisation pond?

Question: What is a reason why the water from a water stabilisation pond may be unusable?
Passage: Solar power is anticipated to become the world's largest source of electricity by 2050, with solar photovoltaics and concentrated solar power contributing 16 and 11 percent to the global overall consumption, respectively.

Question: By what year is solar power expected to become the world's greatest source of electricity?

Question: When is solar power is foreseen to become the largest source of electricity?
Passage: Commercial CSP plants were first developed in the 1980s. Since 1985 the eventually 354 MW SEGS CSP installation, in the Mojave Desert of California, is the largest solar power plant in the world. Other large CSP plants include the 150 MW Solnova Solar Power Station and the 100 MW Andasol solar power station, both in Spain. The 250 MW Agua Caliente Solar Project, in the United States, and the 221 MW Charanka Solar Park in India, are the world’s largest photovoltaic plants. Solar projects exceeding 1 GW are being developed, but most of the deployed photovoltaics are in small rooftop arrays of less than 5 kW, which are grid connected using net metering and/or a feed-in tariff. In 2013 solar generated less than 1% of the worlds total grid electricity.

Question: The largest solar power plant in the world is located in what desert?

Question: Less than 1% of the world's total grid electricity was generated by solar energy in what year?

Question: What is the largest solar power plant in the world?

Question: Where is the largest solar power plant in the world located?

Question: What are the largest photovoltaic solar power plants?
Passage: In the last two decades, photovoltaics (PV), also known as solar PV, has evolved from a pure niche market of small scale applications towards becoming a mainstream electricity source. A solar cell is a device that converts light directly into electricity using the photoelectric effect. The first solar cell was constructed by Charles Fritts in the 1880s. In 1931 a German engineer, Dr Bruno Lange, developed a photo cell using silver selenide in place of copper oxide. Although the prototype selenium cells converted less than 1% of incident light into electricity, both Ernst Werner von Siemens and James Clerk Maxwell recognized the importance of this discovery. Following the work of Russell Ohl in the 1940s, researchers Gerald Pearson, Calvin Fuller and Daryl Chapin created the crystalline silicon solar cell in 1954. These early solar cells cost 286 USD/watt and reached efficiencies of 4.5–6%. By 2012 available efficiencies exceed 20% and the maximum efficiency of research photovoltaics is over 40%.

Question: In the 1880s, who constructed the first solar cell?

Question: In what year was the crystalline silicon solar cell constructed?

Question: What has happened to photovoltaic in the past 20 years?

Question: What is a solar cell?

Question: Who created the first solar cell?

Question: Who created the first solar cell using silver selenide in place of copper oxide?

Question: Who created the crystalline silicon solar cell?
Passage: Concentrating Solar Power (CSP) systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. The concentrated heat is then used as a heat source for a conventional power plant. A wide range of concentrating technologies exists; the most developed are the parabolic trough, the concentrating linear fresnel reflector, the Stirling dish and the solar power tower. Various techniques are used to track the Sun and focus light. In all of these systems a working fluid is heated by the concentrated sunlight, and is then used for power generation or energy storage.

Question: In all the different CSP systems, concentrated sunlight is used to heat what?

Question: What do Concentrating Solar Power systems use?

Question: What is the heat generated from a Concentrating Solar Power system used for?

Question: What is one of the most developed Concentrating Solar Power technologies?

Question: What do Concentrating Solar Power technologies have in common?