The springs served as a source of warmth and cleansing, their minerals as a source of healing. While people still soak in shallow pools heated by the earth, engineers are developing technologies that will allow us to probe more than 10 miles below the earth's surface in search of geothermal energy. We invite you to study the timeline of the recent history of geothermal energy in the United States. As European settlers moved westward across the continent, they gravitated toward these springs of warmth and vitality.
In , the first European to visit the Yellowstone area, John Colter, probably encountered hot springs, leading to the designation "Colter's Hell. William Bell Elliot, a member of John C. Fremont's survey party, stumbles upon a steaming valley just north of what is now San Francisco, California.
Elliot calls the area The Geysers—a misnomer—and thinks he has found the gates of Hell. Guests include J. Pierpont Morgan, Ulysses S. Grant, Theodore Roosevelt, and Mark Twain. At springs located southeast of The Geysers, businessman Sam Brannan pours an estimated half million dollars into an extravagant development dubbed "Calistoga," replete with hotel, bathhouses, skating pavilion, and racetrack. Brannan's was one of many spas reminiscent of those of Europe. Homes and dwellings have been built near springs through the millennia to take advantage of the natural heat of these geothermal springs, but the construction of the Hot Lake Hotel near La Grande, Oregon, marks the first time that the energy from hot springs is used on a large scale.
Folks in Boise, Idaho, feel the heat of the world's first district heating system as water is piped from hot springs to town buildings. Within a few years, the system is serving homes and 40 downtown businesses. Today, there are four district heating systems in Boise that provide heat to over 5 million square feet of residential, business, and governmental space.
Although no one imitated this system for some 70 years, there are now 17 district heating systems in the United States and dozens more around the world. Prince Piero Ginori Conti invents the first geothermal power plant at the Larderello dry steam field in Tuscany, Italy. John D. Grant drills a well at The Geysers with the intention of generating electricity.
This effort is unsuccessful, but one year later Grant meets with success across the valley at another site, and the United States' first geothermal power plant goes into operation. Grant uses steam from the first well to build a second well, and, several wells later, the operation is producing kilowatts, enough electricity to light the buildings and streets at the resort. The plant, however, is not competitive with other sources of power, and it soon falls into disuse.
The first commercial greenhouse use of geothermal energy is undertaken in Boise, Idaho. The operation uses a foot well drilled in Today, more than DHEs are in use around the country. Geothermal technology moves east when Professor Carl Nielsen of Ohio State University develops the first ground-source heat pump, for use at his residence. Krocker, an engineer in Portland, Oregon, pioneers the first commercial building use of a groundwater heat pump.
Greenhouse-style solar ovens use the system invented by de Saussure discussed above. These have glass doors that allow sunlight in, but seal tightly to minimize the escape of heat. The interior of the cookers is black to maximize the absorption of light.
Some of the greenhouse-type cookers also have attached reflective mirrors to help concentrate the light. Solar cookers require no fuel. There are two advantages to this. Fuel is often scarce in poor countries. Kerosene is expensive and firewood, charcoal, dried manure, etc. Second, cooking fuels often burn in a very dirty way, causing much soot and smoke. This creates real health problems, particularly for women and children in countries with traditions of cooking in houses that have poor ventilation.
They state, "The World Health Organization WHO estimates that exposure to smoke from the simple act of cooking is the fifth worst risk factor for disease in developing countries, and causes almost two million premature deaths per year — exceeding deaths attributable to malaria or tuberculosis.
In addition, tens of millions more fall sick with illnesses that could readily be prevented with increased adoption of clean and efficient cooking solutions. Cuker Provenance: Picture taken by module author Dr.
Benjamin Cuker, Hampton University Reuse: You are free to: Share — copy and redistribute the material in any medium or format Adapt — remix, transform, and build upon the material Under the following terms: Attribution — You must give appropriate credit, provide a link to the license, and indicate if changes were made.
You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use. NonCommercial — You may not use the material for commercial purposes. ShareAlike — If you remix, transform, or build upon the material, you must distribute your contributions under the same license as the original. A kitchen can be blackened by soot from an indoor stove that has no chimney.
This photo was taken in Bali, Indonesia in and is typical of rural kitchens in that country. Imagine the effects the smoke has on the health of cooks. Photo by B. Traditional solid fuels also cause severe environmental damage. Forests are often destroyed by the removal of wood for cooking. And the polluting smoke and soot that are indoor health hazards also enter the atmosphere to cause general air pollution. Considering that about 3 billion people, or three out of every seven people on Earth, eat meals prepared on dirty open cookstoves, the pollution adds up quickly.
The developing nations with the worst poverty tend to be found in sunny subtropical climates that fit well with solar cooking. Solar cooking also has its place in wealthier nations. Why heat up the kitchen baking in a traditional gas or electric oven on a hot summer day when a solar cooker will do the job outdoors in an hour or less?
Prior to about , most people in the United States dried their laundry by hanging it on lines. Almost every dwelling had laundry lines. In rural and suburban areas they were typical features of side yards or backyards. In cities the lines were often run between adjacent apartment buildings. A pulley system allowed one to work out of a window to add and remove items held on with clothespins. In colder and wetter climates, basements and back porches provided good drying spots, as well as indoor racks in kitchens or laundry rooms.
Now most people in the United States use electricity or gas to dry laundry. Once a common feature of the human landscape, laundry lines are now a rare sight in the United States. Many communities have banned outdoor drying of laundry. The argument is that hanging clothes is an eyesore that lowers property values — it makes the community look "poor.
Local organizations around the United States work to overturn prohibitions on outdoor laundry drying. One national organization is called Project Laundry List. Usually electricity or gas is used to heat water in tanks.
But it was not always this way. Until the early 20th century, hot water on demand from a faucet was a rare luxury. In households were still transitioning to indoor plumbing in many parts of the United States. To make hot water for washing and bathing, most people had to heat large pots on stoves.
Some stand-alone hot water heaters were available, but had to be lit by hand for each use, and carefully monitored so as not to explode.
Prior to the modern electric or gas hot water heater, a company from sunny California sold the first commercial solar hot water system in , called the "Climax. The solar-powered Climax consisted of a set of black tanks in a glass-covered box placed on the roof. Thousands were sold, but they tended to cool off quickly at night.
In , William J. Bailey brought to market an improved design that separated the collection of solar energy to a glass-covered box of small tubes. This allowed the storage tank to be insulated and preserve its heat throughout the night.
Bailey's design quickly replaced the Climax and was standard on many houses built in Florida in the s. Bailey's design is the basis for modern systems. The "energy crisis" resulting from a war in the Middle East renewed interest in all things solar in the United States. Solar hot water systems reappeared on the market in the late s. They all consisted of two basic parts, a collector panel and a storage tank.
The collector panel contained a system of small black pipes on a black background, and was covered with glass. A pump would then circulate the heated water to an insulated storage tank. At night the pumps would turn off and allow all of the water to drain out of the panel — an important feature in places where temperatures dropped below the freezing point of water at night. When water freezes, it expands and will break the pipes. The drain back systems worked well in places free of frost, but at higher latitudes many failed due to incomplete drainage at night.
Provenance: Photo taken by B. The more common installation today uses a pressurized mix of glycol and water like antifreeze used in automobile engines to transfer the heat between the collector and storage tank. A heat exchanger transfers the thermal energy to the tank. This system requires a pump to circulate the heated antifreeze mixture between the solar collector and the tank.
Once it arrives at the tank, the hot antifreeze passes through a system of small pipes on either on the side of the steel tank, or running through it. This is the heat exchanger that transfers thermal energy from the antifreeze to the copper pipe and from the pipe to the water in the storage tank.
There are thermal sensors located in the tank and at the solar collector. A small computer in the controller will turn on the pump when temperatures in the collector exceed the temperature in the tank by about 8 o C. When controller temperature drops due to cloud cover or approaching night, the controller stops the circulating pump.
Temperatures may reach o F at the collector. Typically traditional hot water heaters are kept between o and o F, but solar-powered tanks are set to go as high as o F to maximize capacity for periods when the sun is not shining. Sometimes a series of cloudy days will exhaust the supply of stored hot water. A backup electric resistance heater coil built into the tank will ensure a supply of hot water until the sunshine returns. Safety considerations — All tank-type water heaters have three safety considerations.
First, as the water is heated, it expands, and the resulting pressure could cause the tank to explode. A pressure relief valve at the top of the tanks protects against this. Second, the hot water can also cause scalding burns to the user, so temperatures must be set low enough to prevent this.
Finally, a tank with too low of a temperature can encourage the growth of pathogenic bacteria like the one that causes Legionnaires' disease. So it is best if tanks are kept at a minimum of 60 o C o F , but the water should be distributed at 50 o C o F. Solar hot water systems get all of their energy from the sun, except that small amount used to power the circulating pump and run the small computer and sensor system. Solar hot water systems are therefore the most sustainable choice to make.
However, they are expensive to install, costing usually about four or five times as much as traditional electric or natural gas systems. An alternative approach is to install a tankless or on-demand system heated by electricity or natural gas. Traditional tank systems lose much of the energy from the storage tank by conduction, convection, and radiation.
The tankless systems only turn on when the hot water faucet is opened. This saves on the loss of heat from a storage tank. Solar energy can be used to heat buildings. Ancient architects understood how building and positioning structures could take advantage of solar resources. Such passive designs are covered in a different unit. Here we will focus mostly on active designs for space heating. In French engineer Felix Trombe used an design of Edward Morse to create a thermal—siphon device to heat homes.
This appliance combines the greenhouse effect, convection, and heat storage by a solid. A concrete or stone wall is built right next to an existing sun-facing wall. Glazing of glass or clear plastic is placed over the wall with an air gap of a few centimeters.
This is the familiar greenhouse concept. Holes are placed in the concrete wall at the top and the bottom. These holes are connected to short lengths of pipe that extend to the inside of the building. When sunlight heats the wall, it causes the air to expand and float up to the top, where the warm air then exits into the building. This warm air is replaced by cool air from the building drawn in to the bottom of the wall through the lower set of pipes.
Simple thermal air siphons also can be added to existing windows. These devices also combine the greenhouse effect with natural passive convection. The collector can be set to have a more effective angle for collecting sunlight.
Including a small solar powered fan, like those used to cool desktop computers, will make the unit more efficient. Care must be taken in insulation to seal around the gaps created in the double hung windows. Otherwise any heat gain will be lost by penetration of cold air through the leaks.
Temperatures may reach deg. The active solar hot water systems discussed above form the basis for another way to provide space heating. Essentially a solar hot water system is sized to meet much or most of the space-heating needs for the building.
This means many more collector panels, and increased tank storage capacity. Such systems work best when used with radiant floor heating hydronic.
Radiant floor heating uses small copper or plastic tubing to pass the heated fluid usually glycol solution under the flooring material.
The hot tubing heats the floor from beneath, and the flooring in turn radiates the heat into the space above. This works best for wood or tile floors, as carpeting insulates the floor. For an existing structure that is not on a slab there is a basement or crawl space , this requires stapling the tubing to the bottom side of the floor and adding insulation under the tubing. Radiant floor heating works best with most solar hot water systems because such systems produce fluid temperatures in the winter of only — o F.
Recall that the rate of heat flow between objects is proportional to the difference in temperature. To transfer enough heat into the building, the radiating surface must be large, as is the case with radiant floor systems. Baseboard or old-fashioned cast iron radiators would not supply enough area for radiation at these temperatures. They are designed to work at the higher temperatures achieved by using natural gas or heating oil as the source of energy.
However, it is possible to achieve higher temperatures with solar hot water systems using a different type of collector. Evacuated tube collectors coupled with heat pipes are more efficient than traditional flat plate greenhouse-type collectors. This can be a tough one for people to wrap their heads around sometimes. James Prescott Joule, after whom the unit of heat energy is named, was experimenting with fluids and he found that when he agitated the fluid, its temperature increased.
He and his team then performed mechanical work on a float and in doing so converted that mechanical energy to thermal energy! Topics: Thermal Management. Blog Contact an Expert. It's not what you think
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