TIPS ON SOLAR HEATING
WHAT IS SOLAR HEATING?
The amount of solar energy (insolation) that comes into a building through the windows (size, orientation, glazing, and shading) depends on time of year, location, and percentage sunshine (clouds and haze).
The solar heating can be estimated from tables of clear-day insolation by latitude and percentage sunshine by month. Average insolation values by month that take into account cloud cover for different angles of surfaces are available on the Internet.
The data for vertical insolation indicate that in most locations vertical windows on the south can be net heat gainers, depending on climate and R value of the windows. Surprisingly, even single-pane windows on the south can be net energy gainers in temperate climates.
Also, during the summer vertical windows let in less solar energy due to the angle of the sun (cosine factor). There is more reflection due to the larger angle of incidence.
Example 5.1
Calculate the amount of solar heat that comes through a south-facing window (single pane) for January (70% sunshine).
Vertical window, 1.2 by 2.5 m, single pane, transmission = 90%
Area = 3 m2, insolation for January is 6 kWh/m2 per clear day
Energy hitting window per day = 3 m2 * 6 kWh/m2 = 18 kWh/day
Energy transmitted = 0.9 * 18 kWh/day = 16 kWh/day = 55,000 Btu/day
Energy for month = 16 kWh/day * 31 days * 0.70 = 350 kWh = 1.2 * 106 Btu
Maps of solar insolation for the United States by month are available from the National Renewable Energy Laboratory (NREL) for different types of collectors and orientation (http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/). The two-axis concentrating collector gives the normal to the sun. The maps also take into account the percentage sunshine, so the average values of energy per day do not have to be adjusted.
Thursday, December 25, 2014
ENERGY PRODUCTION OF OUR SUN BASIC INFORMATION
How much energy is produced in the sun?
The energy produced by nuclear reactions in the interior of the Sun must equal the amount of energy radiated from the surface, since otherwise the Sun could not have been structurally stable over long periods of time.
Evidence for the stability of the Sun comes from several sources. Stability over a period of nearly 3×10^9 years is implied by the relative stability of the temperature at the Earth’s surface (oxidised sediments and fossil remains indicate that water in its fluid phase has been present throughout such periods).
Stability over an even longer time is implicit in our understanding of the evolution of the Sun and other similar stars. As an indication of this stability, the variations in the radius of the Sun believed to have taken place since its assumed formation from clouds of dust and gas.
The conversion of energy contained in the atomic constituents of mainsequence stars such as the Sun from heat of nuclear reactions (which transforms hydrogen into helium) to radiation escaping from the surface is largely understood.
The basis for regarding such radiation as a renewable source is that it may continue essentially unaltered for billions of years. Yet there is also a possibility of tiny variations in solar energy production that may have profound implications for life on the planets encircling it.
The energy produced by nuclear reactions in the interior of the Sun must equal the amount of energy radiated from the surface, since otherwise the Sun could not have been structurally stable over long periods of time.
Evidence for the stability of the Sun comes from several sources. Stability over a period of nearly 3×10^9 years is implied by the relative stability of the temperature at the Earth’s surface (oxidised sediments and fossil remains indicate that water in its fluid phase has been present throughout such periods).
Stability over an even longer time is implicit in our understanding of the evolution of the Sun and other similar stars. As an indication of this stability, the variations in the radius of the Sun believed to have taken place since its assumed formation from clouds of dust and gas.
The conversion of energy contained in the atomic constituents of mainsequence stars such as the Sun from heat of nuclear reactions (which transforms hydrogen into helium) to radiation escaping from the surface is largely understood.
The basis for regarding such radiation as a renewable source is that it may continue essentially unaltered for billions of years. Yet there is also a possibility of tiny variations in solar energy production that may have profound implications for life on the planets encircling it.
Sunday, November 9, 2014
WHAT IS RENEWABLE ENERGY? RENEWABLE ENERGY BASIC INFORMATION AND TUTORIALS
RENEWABLE ENERGY
Solar energy is referred to as renewable or sustainable energy because it will be available as long as the sun continues to shine. Estimates for the remaining life of the main stage of the sun are another 4 to 5 billion years.
The energy from the sun, electromagnetic radiation, is referred to as insolation. The other main renewable energies are wind, bioenergy, geothermal, hydro, tides, and waves.
Wind energy is derived from the uneven heating of the surface of the Earth due to more heat input at the equator with the accompanying transfer of water and thermal energy by evaporation and precipitation.
In this sense, rivers and dams for hydro energy are stored solar energy. The third major aspect of solar energy is the conversion of solar energy into biomass by photosynthesis.
Animal products such as oil from fat and biogas from manure are derived from solar energy. Another renewable energy is geothermal energy due to heat from the Earth from decay of radioactive particles and residual heat from gravitation during formation of the Earth.
Volcanoes are fiery examples of geothermal energy reaching the surface from the interior, which is hotter than the surface. Tidal energy is primarily due to the gravitational interaction of the Earth and the moon.
Overall 14% of the world’s energy comes from bioenergy, primarily wood and charcoal but also crop residue and even animal dung for cooking and some heating. This contributes to deforestation and the loss of topsoil in developing countries. Production of ethanol from biomass is now a contributor to liquid fuels for transportation, especially in Brazil and the United States.
In contrast, fossil fuels are stored solar energy from past geological ages. Even though the quantities of oil, natural gas, and coal are large, they are finite, and for the long term of hundreds of years, they are not sustainable.
ADVANTAGES/DISADVANTAGES
The advantages of renewable energy are that they are sustainable (nondepletable), ubiquitous (found everywhere across the world, in contrast to fossil fuels and minerals), and essentially nonpolluting. Note that wind turbines and photovoltaic panels do not need water for the generation of electricity, in contrast to steam plants fired by fossil fuels and nuclear power.
The disadvantages of renewable energy are variability and low density, which in general results in higher initial cost. For different forms of renewable energy, other disadvantages or perceived problems are visual pollution, odor from biomass, avian and bat mortality with wind turbines, and brine from geothermal energy.
Wherever a large renewable facility is to be located, there will be perceived and real problems to the local people. For conventional power plants using fossil fuels, for nuclear energy, and even for renewable energy, there is the problem of “not in my backyard.”
ECONOMICS OF RENEWABLE ENERGY
Business entities always couch their concerns in terms of economics (money), such as “We cannot have a clean environment because it is uneconomical.” The thought here is that renewable energy is not economical in comparison to coal, oil, and natural gas.
We must be allowed to continue our operations as in the past because if we have to install new equipment to reduce greenhouse gas emissions, we cannot compete with other energy sources, and finally we will have to reduce employment, jobs will go overseas, and so on.
The different types of economics to consider are pecuniary, social, and physical. Pecuniary is what everybody thinks of as economics, money. On that note, we should be looking at life-cycle costs rather than our ordinary way of doing business, low initial costs. Life-cycle costs refer to all costs over the lifetime of the system.
Social economics are those borne by everybody, and many businesses want the general public to pay for their environmental costs. A good example is the use of coal in China, where there are laws (social) for clean air, but they are not enforced.
The cost will be paid in the future in terms of health problems, especially for the children today. If environmental problems affect someone else today or in the future, who pays? The estimates of the pollution costs for generation of electricity by coal range from $0.005 to $0.10/kWh.
Physical economics is the energy cost and the efficiency of the process. There are fundamental limitations in nature due to physical laws. Energetics, which is the energy input versus energy in the final product for any source, should be positive.
For example, production of ethanol from irrigated corn has close to zero energetics. So, physical economics is the final arbitrator in energy production and consumption. In the end, Mother Nature always wins, or the corollary, pay now or probably pay more in the future.
Finally, we should look at incentives and penalties for the energy entities. What each entity wants are subsidies for itself and penalties for its competitors. Penalties come in the form of taxes and environmental and other regulations, while incentives come in the form of subsidies, breaks on taxes, lack of social costs to pay on the product, and governmental funding of research and development.
How much should we subsidize businesses for exporting overseas? It is estimated that we use energy sources in direct proportion to the incentives that source has received in the past. There are many examples of incentives and penalties for all types of energy production and use.
Solar energy is referred to as renewable or sustainable energy because it will be available as long as the sun continues to shine. Estimates for the remaining life of the main stage of the sun are another 4 to 5 billion years.
The energy from the sun, electromagnetic radiation, is referred to as insolation. The other main renewable energies are wind, bioenergy, geothermal, hydro, tides, and waves.
Wind energy is derived from the uneven heating of the surface of the Earth due to more heat input at the equator with the accompanying transfer of water and thermal energy by evaporation and precipitation.
In this sense, rivers and dams for hydro energy are stored solar energy. The third major aspect of solar energy is the conversion of solar energy into biomass by photosynthesis.
Animal products such as oil from fat and biogas from manure are derived from solar energy. Another renewable energy is geothermal energy due to heat from the Earth from decay of radioactive particles and residual heat from gravitation during formation of the Earth.
Volcanoes are fiery examples of geothermal energy reaching the surface from the interior, which is hotter than the surface. Tidal energy is primarily due to the gravitational interaction of the Earth and the moon.
Overall 14% of the world’s energy comes from bioenergy, primarily wood and charcoal but also crop residue and even animal dung for cooking and some heating. This contributes to deforestation and the loss of topsoil in developing countries. Production of ethanol from biomass is now a contributor to liquid fuels for transportation, especially in Brazil and the United States.
In contrast, fossil fuels are stored solar energy from past geological ages. Even though the quantities of oil, natural gas, and coal are large, they are finite, and for the long term of hundreds of years, they are not sustainable.
ADVANTAGES/DISADVANTAGES
The advantages of renewable energy are that they are sustainable (nondepletable), ubiquitous (found everywhere across the world, in contrast to fossil fuels and minerals), and essentially nonpolluting. Note that wind turbines and photovoltaic panels do not need water for the generation of electricity, in contrast to steam plants fired by fossil fuels and nuclear power.
The disadvantages of renewable energy are variability and low density, which in general results in higher initial cost. For different forms of renewable energy, other disadvantages or perceived problems are visual pollution, odor from biomass, avian and bat mortality with wind turbines, and brine from geothermal energy.
Wherever a large renewable facility is to be located, there will be perceived and real problems to the local people. For conventional power plants using fossil fuels, for nuclear energy, and even for renewable energy, there is the problem of “not in my backyard.”
ECONOMICS OF RENEWABLE ENERGY
Business entities always couch their concerns in terms of economics (money), such as “We cannot have a clean environment because it is uneconomical.” The thought here is that renewable energy is not economical in comparison to coal, oil, and natural gas.
We must be allowed to continue our operations as in the past because if we have to install new equipment to reduce greenhouse gas emissions, we cannot compete with other energy sources, and finally we will have to reduce employment, jobs will go overseas, and so on.
The different types of economics to consider are pecuniary, social, and physical. Pecuniary is what everybody thinks of as economics, money. On that note, we should be looking at life-cycle costs rather than our ordinary way of doing business, low initial costs. Life-cycle costs refer to all costs over the lifetime of the system.
Social economics are those borne by everybody, and many businesses want the general public to pay for their environmental costs. A good example is the use of coal in China, where there are laws (social) for clean air, but they are not enforced.
The cost will be paid in the future in terms of health problems, especially for the children today. If environmental problems affect someone else today or in the future, who pays? The estimates of the pollution costs for generation of electricity by coal range from $0.005 to $0.10/kWh.
Physical economics is the energy cost and the efficiency of the process. There are fundamental limitations in nature due to physical laws. Energetics, which is the energy input versus energy in the final product for any source, should be positive.
For example, production of ethanol from irrigated corn has close to zero energetics. So, physical economics is the final arbitrator in energy production and consumption. In the end, Mother Nature always wins, or the corollary, pay now or probably pay more in the future.
Finally, we should look at incentives and penalties for the energy entities. What each entity wants are subsidies for itself and penalties for its competitors. Penalties come in the form of taxes and environmental and other regulations, while incentives come in the form of subsidies, breaks on taxes, lack of social costs to pay on the product, and governmental funding of research and development.
How much should we subsidize businesses for exporting overseas? It is estimated that we use energy sources in direct proportion to the incentives that source has received in the past. There are many examples of incentives and penalties for all types of energy production and use.
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