Here’s how they work.Heat in a solar thermal system is guided by five basic principles: heat gain; heat transfer; heat storage; heat transport; and heat insulation.[53] Here, heat is the measure of the amount of thermal energy an object contains and is determined by the temperature, mass and specific heat of the object. Solar thermal power plants use heat exchangers that are designed for constant working conditions, to provide heat exchange. Copper heat exchangers are important in solar thermal heating and cooling systems because of copper’s high thermal conductivity, resistance to atmospheric and water corrosion, sealing and joining by soldering, and mechanical strength. Copper is used both in receivers and in primary circuits (pipes and heat exchangers for water tanks) of solar thermal water systems.[54] Heat gain is the heat accumulated from the sun in the system. Solar thermal heat is trapped using the greenhouse effect; the greenhouse effect in this case is the ability of a reflective surface to transmit short wave radiation and reflect long wave radiation. Heat and infrared radiation (IR) are produced when short wave radiation light hits the absorber plate, which is then trapped inside the collector. Fluid, usually water, in the absorber tubes collect the trapped heat and transfer it to a heat storage vault. Heat is transferred either by conduction or convection. When water is heated, kinetic energy is transferred by conduction to water molecules throughout the medium. These molecules spread their thermal energy by conduction and occupy more space than the cold slow moving molecules above them. The distribution of energy from the rising hot water to the sinking cold water contributes to the convection process. Heat is transferred from the absorber plates of the collector in the fluid by conduction. The collector fluid is circulated through the carrier pipes to the heat transfer vault. Inside the vault, heat is transferred throughout the medium through convection. Heat storage enables solar thermal plants to produce electricity during hours without sunlight. Heat is transferred to a thermal storage medium in an insulated reservoir during hours with sunlight, and is withdrawn for power generation during hours lacking sunlight. Thermal storage mediums will be discussed in a heat storage section. Rate of heat transfer is related to the conductive and convection medium as well as the temperature differences. Bodies with large temperature differences transfer heat faster than bodies with lower temperature differences. Heat transport refers to the activity in which heat from a solar collector is transported to the heat storage vault. Heat insulation is vital in both heat transport tubing as well as the storage vault. It prevents heat loss, which in turn relates to energy loss, or decrease in the efficiency of the system. Heat storage for electric base loads[edit] Main article: Thermal energy storage Heat storage allows a solar thermal plant to produce electricity at night and on overcast days. This allows the use of solar power for baseload generation as well as peak power generation, with the potential of displacing both coal- and natural gas-fired power plants. Additionally, the utilization of the generator is higher which reduces cost. Even short term storage can help by smoothing out the “duck curve” of rapid change in generation requirements at sunset when a grid includes large amounts of solar capacity. Heat is transferred to a thermal storage medium in an insulated reservoir during the day, and withdrawn for power generation at night. Thermal storage media include pressurized steam, concrete, a variety of phase change materials, and molten salts such as calcium, sodium and potassium nitrate.[55][56] Steam accumulator[edit] The PS10 solar power tower stores heat in tanks as pressurized steam at 50 bar and 285 °C. The steam condenses and flashes back to steam, when pressure is lowered. Storage is for one hour. It is suggested that longer storage is possible, but that has not been proven in an existing power plant.[57] Molten salt storage[edit] See also: Thermal energy storage The 150 MW Andasol solar power station is a commercial parabolic trough solar thermal power plant, located in Spain. The Andasol plant uses tanks of molten salt to store solar energy so that it can continue generating electricity even when the sun isn’t shining.[58] A variety of fluids have been tested to transport the sun’s heat, including water, air, oil, and sodium, but Rockwell International[59] selected molten salt as best.[60] Molten salt is used in solar power tower systems because it is liquid at atmospheric pressure, provides a low-cost medium to store thermal energy, its operating temperatures are compatible with today’s steam turbines, and it is non-flammable and nontoxic. Molten salt is used in the chemical and metals industries to transport heat, so industry has experience with it. The first commercial molten salt mixture was a common form of saltpeter, 60% sodium nitrate and 40% potassium nitrate. Saltpeter melts at 220 °C (430 °F) and is kept liquid at 290 °C (550 °F) in an insulated storage tank. Calcium nitrate can reduce the melting point to 131 °C, permitting more energy to be extracted before the salt freezes. There are now several technical calcium nitrate grades stable at more than 500 °C. This solar power system can generate power in cloudy weather or at night using the heat in the tank of hot salt. The tanks are insulated, able to store heat for a week. Tanks that power a 100-megawatt turbine for four hours would be about 9 m (30 ft) tall and 24 m (80 ft) in diameter. The Andasol power plant in Spain is the first commercial solar thermal power plant using molten salt for heat storage and nighttime generation. It came on line March 2009.[61] On July 4, 2011, a company in Spain celebrated an historic moment for the solar industry: Torresol’s 19.9 MW concentrating solar power plant became the first ever to generate uninterrupted electricity for 24 hours straight, using a molten salt heat storage.[62] In 2016 SolarReserve proposed a 2 GW, $5 billion concentrated solar plant with storage in Nevada. In January 2019 Shouhang Energy Saving Dunhuang 100MW molten salt tower solar energy photothermal power station project was connected to grid and started operating. Its configuration includes an 11-hour molten salt heat storage system and can generate power consecutively for 24 hours.[63] Phase-change materials for storage[edit] Phase Change Material (PCMs) offer an alternative solution in energy storage.[64] Using a similar heat transfer infrastructure, PCMs have the potential of providing a more efficient means of storage. PCMs can be either organic or inorganic materials. Advantages of organic PCMs include no corrosives, low or no undercooling, and chemical and thermal stability. Disadvantages include low phase-change enthalpy, low thermal conductivity, and flammability. Inorganics are advantageous with greater phase-change enthalpy, but exhibit disadvantages with undercooling, corrosion, phase separation, and lack of thermal stability. The greater phase-change enthalpy in inorganic PCMs make hydrate salts a strong candidate in the solar energy storage field.[65] Use of water[edit] A design which requires water for condensation or cooling may conflict with location of solar thermal plants in desert areas with good solar radiation but limited water resources. The conflict is illustrated by plans of Solar Millennium, a German company, to build a plant in the Amargosa Valley of Nevada which would require 20% of the water available in the area. Some other projected plants by the same and other companies in the Mojave Desert of California may also be affected by difficulty in obtaining adequate and appropriate water rights. California water law currently prohibits use of potable water for cooling.[66] Other designs require less water. The Ivanpah Solar Power Facility in south-eastern California conserves scarce desert water by using air-cooling to convert the steam back into water. Compared to conventional wet-cooling, this results in a 90% reduction in water usage at the cost of some loss of efficiency. The water is then returned to the boiler in a closed process which is environmentally friendly.[67] Conversion rates from solar energy to electrical energy[edit] Of all of these technologies the solar dish/Stirling engine has the highest energy efficiency. A single solar dish-Stirling engine installed at Sandia National Laboratories National Solar Thermal Test Facility (NSTTF) produces as much as 25 kW of electricity, with a conversion efficiency of 31.25%.[68] Solar parabolic trough plants have been built with efficiencies of about 20%.[citation needed] Fresnel reflectors have an efficiency that is slightly lower (but this is compensated by the denser packing). The gross conversion efficiencies (taking into account that the solar dishes or troughs occupy only a fraction of the total area of the power plant) are determined by net generating capacity over the solar energy that falls on the total area of the solar plant. The 500-megawatt (MW) SCE/SES plant would extract about 2.75% of the radiation (1 kW/m²; see Solar power for a discussion) that falls on its 4,500 acres (18.2 km²).[69] For the 50 MW AndaSol Power Plant[70] that is being built in Spain (total area of 1,300×1,500 m = 1.95 km²) gross conversion efficiency comes out at 2.6%. Furthermore, efficiency does not directly relate to cost: on calculating total cost, both efficiency and the cost of construction and maintenance should be taken into account.
when you were little, you used a magnifying glass to aim the sun and burn a leaf. That is solar thermal energy. It can be used to heat water which will run a steam engine and make electricity
When you were a child you used a magnifying glass aimed at the sun to burn a leaf in the garden. That is solar thermal power. It can be used to heat water which will run a steam engine and make electricity.
People around the globe are shifting towards renewable sources of energy to meet their power needs. While solar power is a cost-efficient and effective way to meet the world’s power requirements, the important factor to consider is whether solar panels can really make sense in the areas of shade.
Do solar panel works in shade? Yes, Solar panels can work in shaded areas as well as during cloudy days but their output power capacity is compromised due to less exposure to sunlight. Certain solutions like solar panel design and roof orientation can help prevent an excessive power loss caused due to less sunlight exposure.
People generally assume that solar panels are of no use unless exposed to bright sunlight. However, this is a misconception and modern solar panels are capable enough to work even in poor light conditions. Still, there is a need to analyze the effect of shade on the solar panel as well as how you can minimize it and what sort of panel design is right for fulfilling your power needs given the shading conditions of your location. In this article, we will examine the sources of shading, its effects on the efficiency of the solar panel and how the efficiency losses can be mitigated.
What causes shading and does it affect solar panels?
As discussed above, shading plays a very crucial part in the efficiency of the solar panels. There are different sources that can be a cause of shade on solar panels. The most common sources are listed below:
Trees – Many residential areas that are located in green spaces face shading issues. The trees near the solar panel setups can cause shading issues by encroaching the setups.
Clouds – Weather plays a very important factor in determining the amount of sunlight reaching the solar panels. Clouds do not completely block the sunlight but they do reduce the amount of sunlight exposure on to the panel which reduces the amount of solar energy harvested to electricity
Other Panels – Solar panels can also be shaded by neighboring panels especially when there are ground installations. If incorrectly installed, nearby panels can caste a shade on the panels in the same system.
Roof and Buildings – Panels are greatly affected by the roofs and surrounding buildings if the system is located in an overly populated area. Based on the peak hours of the day, surrounding buildings and roofs can block sunlight to the panels
Now that we have looked at the sources of shading lets discuss the impact it has on the solar panels.
Decrease in Efficiency-A solar panel consists of the solar cells. Those solar cells which are covered in shade will stop working so if 50% of the panel’s solar cells are under shade, then solar panel’s efficiency will be reduced to half but shading does not completely halt the electricity production. Most of the modern solar panels can work even in poor light conditions but at the expense of efficiency. The power loss varies based on the amount of shade the panels are facing.
If you cannot avoid shade, then the best option is to use the shade tolerant solar cells like Uni-solar etc.
Shortens life span –When some of the solar cells in a solar panel are not working due to shading then other cells free of shade work harder in order to compensate the power losses. In this process, the unshaded solar cells might get overheated or burn out due to over performing. This reduces the lifetime of the solar panel and can result in permanent damage to the PV system. Bypass diodes can be used to minimize the effect of partial shading on the solar panel.
Do solar panels need direct sunlight to make sense?
A lot of people wonder whether direct sunlight is needed for solar to make it a feasible option economically or not. Yes, indeed, the more sun exposure there is, then more output gets generated from the panels. It is true that direct sunlight provides optimum conditions for the panel to operate however even in the cloudy weather, some of the light may still reach your solar panels to make them work.
It is estimated that a solar panel will be 40% less effective during cloudy weather conditions.
In a grid-tied solar panel, the excess amount of power generated during a sunny day, gets fed back to the utility grid in exchange of energy credits. This is done via a device known as a net meter which measures the electricity going to and from the grid. The energy credits can be utilized to draw power at night and on a cloudy day.
The term “Peak sun hours” refers to hours during which the intensity of sunlight is maximum, i.e., 1,000 watts per square meter. Peak sun hours provide an accurate description of how much energy your panels can produce in a day.
On average, the peak sun hours are between 3 to 4 hours a day.
How do you calculate how many sun-hours an area gets?
Solar map tools can be used to estimate the average amount of sun hours of a location however it only gives you the estimate based on longitude and latitude coordinates of a location. In order to get an accurate reading many other factors about a location should be taken into consideration before drawing any conclusions.
Some software tools like Aurora can use the satellite imagery of a location and estimate the sun hours based off that information alone. But these tools are not always 100% accurate and it takes a lot of time to learn how to use them if you’re not all that computer savvy.
Solar installation companies, on the other hand, should have their own proprietary software that can also provide an accurate estimation of sun hours of a location to its customers based on factors like roof orientation, shading, weather etc. Many other metrics can be estimated from the solar energy analysis of a location such as a target offset of solar energy and estimates of 20 to 30-year savings.
Solar companies usually provide an on-site investigation once you sign up to go solar with them. These companies have certified solar techs who uses a tool called “sun eye” to provide more accurate shading analysis of a location to ensure that the solar panel can meet the companies estimated amount of production on a particular location. If in the event it is determined that your location does have some shading issues, there are certain ways to optimize the solar panel productivity.
How can issues of shading be resolved to boost solar panel productivity?
Solar panel systems can be altered and modified in a number of different ways to overcome shading losses. Some of the common methods devised are as below:
Stringing Arrangements – Modules in a solar panel system are connected in series to form strings that are connected in parallel to an inverter. The power output of a string can be brought down significantly if it has a shaded module in it. However, the output of a parallel string cannot be reduced by a shaded module in one string. Hence the system can be optimized by classifying shaded and unshaded modules into different strings. For example, in systems that are commonly deployed in the market or businesses, modules that receive shade can be grouped into one string while the remaining modules that receive no shade can be grouped into another string.
Bypass Diodes – They are devices in a module in which the current can go past the regions of the module that are covered by shade. Utilization of the bypass diodes allows unshaded cell strings to allow current to flow through them. However, the drawback of using these devices is that we cannot benefit from the working from the solar cells which have been bypassed by the flowing current. Roughly, around 3 bypass diodes will be required for a panel having 60 solar cells.
Module-level Power Electronics (MLPEs) – MLPEs are devices that are connected to each shaded solar panel module in a PV system to boost their power output by the use of maximum power point tracking. MLPEs commonly include DC optimizers and microinverters.
DC Optimizers – DC optimizers tend to increase the power output of an individual solar module, by maintaining the performance of other modules as well, by changing the voltages and current at the output of a particular solar module. For instance, a DC optimizer will boost the output current of a shaded solar panel producing electricity with a lower current by decreasing its voltage so that the current through it is of the same value as the current flowing in the unshaded panels. This ensures that the same amount of power is produced by all the panels.
Microinverters – The DC -AC conversion in each panel can be done by having each panel connected to a small inverter instead of having a single inverter for the entire system since all the modules will be connected in parallel and each microinverter will work at its MPPT, the functioning of other panels would not be affected. This will not let the efficiency of the panels be affected due to the shading effect of the panels.
Ground Mount PV System– In Ground-mounted PV systems, the panel orientation can be optimized as well as there are no space constraints. They also have better ground clearance between the panel and the ground.
I was told by a solar company that I did not qualify because of the pitch of my garage roof. I am very much interested in solar energy for my home. That company suggested ground panels but said it would take up 1/3 of my tiny yard. What are my other options?
Sunrun is the largest residential solar company in the United States with over 250,000 customers over 23 states including operations in Puerto Rico but is their program right for you? We will reveal…
Tesla solar shingles have been one of the most talked-about and anticipated breakthroughs in the solar industry since they were first announced in 2016. The idea that you can power your home with…
. I wanted to inquired about the large sized solar sipper. We recommend them to clients who feed and care for homeless cats in our city. We absolutely love the solar sippers for cat caretakers who need to supply fresh water for outdoor cats but cannot use an electric heated water bowl for lack of an accessible electrical outlet. In years past, I have noticed the solar sippers being offered on Amazon but this year I cannot find them anywhere. Amazon stated that they are out of stock, possibly indefinitely. I was very sad to hear this. Is there any way your customers can still access the large sized solar sipper? We receive questions about this constantly during the cold winter months. I would love to get my hands on them again. If you have any information for me on this subject I would be so grateful. I appreciate your time. Have a lovely day.
Give outdoor creatures the same loving fresh water your indoor pets receive for morning drinking. Solar Sipper Model 10008 portable all season durable easy to clean outdoor water station for wild birds is safe, with no electric wires to chew or peck. Keeps water covered and clean from deadly bacteria. Insulates with air space to keep water warm in winter and cool in summer. Passive solar black top design uses sunlight to keep inner water ice free in ambient wind free outer air to about 20 deg. F. Eight inch diameter holds one quart fresh water. Bird has innovative 1 1/2 inch drinking hole( pet has 4” hole), Berry red outer container attracts birds. Google the tests at solar sipper 21415. Black top painted tanks were used long ago in Old West USA to keep winter drinking water free of ice for prairie cattle.
BETHESDA, Md. – October 14, 2019 – Alley Cat Allies and its supporters around the world will observe Global Cat Day® on Wednesday, October 16, with a commitment to save cats, including stray and feral cats, from being killed.
Becky Robinson, the president and founder of Alley Cat Allies, is asking everyone who values the lives of cats to sign the Alley Cat Allies’ Global Cat Day Pledge online.
“The Global Cat Day Pledge includes the fundamental principle that all cats have the right to live their lives, and it guides everything we do to protect cats,” Robinson said. “We stand for humane, non-lethal programs for cats, and those who join us can take action to stop cats from being killed.”
Millions of cats and kittens are in life-threatening danger because felines are killed more than any other animal in shelters across the nation. Global Cat Day demands that community leaders abolish policies that result in the killing of cats; equip communities with lifesaving, humane policies like Trap-Neuter-Return (TNR); and change any policies that threaten cats’ health and safety.
TNR is the mainstream approach in which community cats, sometimes called feral cats, are humanely trapped, spayed or neutered, vaccinated, eartipped and returned to the outdoor homes where they live and thrive. As sound public policy, TNR reduces shelter intake, “euthanasia” and calls to animal services, which saves taxpayer dollars.
About Alley Cat Allies
Alley Cat Allies, headquartered in Bethesda, Md., is the global engine of change for cats. Alley Cat Allies is the leading advocacy organization dedicated to protecting and improving the lives of all cats through its innovative, cutting-edge programs. Founded in 1990, today Alley Cat Allies has grown into a powerful force with over half a million supporters. The organization has helped and inspired countless individuals, communities and other organizations to save and improve the lives of cats and kittens worldwide. Alley Cat Allies works with lawmakers, animal shelters and advocates to change attitudes and advance lifesaving policies that best serve the interests of cats. Alley Cat Allies’ website is www.alleycat.org, and the organization is active on Facebook, Twitter, Instagram and YouTube.
Dear EarthTalk: What is climate gentrification and where is it happening?
– Jamie B., Boston, MA
Climate gentrification is a relatively new term describing what happens when neighborhoods traditionally overlooked by wealthy people become more attractive—and expensive—given their siting in geographic areas that happen to be more resilient to climate-related threats such as stronger, more frequent hurricanes, flooding, wildfires, etc.
Will the culture of communities like Little Haiti on the slightly elevated outskirts of Miami change as a result of “climate gentrification”? Credit: Knight Foundation, FlickrCC
The already-classic case is in Florida’s Miami-Dade County, where climate-related flooding and sea level rises are driving wealthy homeowners away from once pricey beach-front property and into the higher elevations surrounding areas like Little Haiti, Liberty City and Allapattah that have traditionally been home to struggling minority families. The result is greater density and higher home prices and rents in these recently poor neighborhoods. Meanwhile the locals move out, complaining that the transition is forcing them out of their beloved homes while sapping once vibrant cultural identities.
A recently released Harvard study of real estate values by elevation in the Miami area over the last five decades found that while home prices were rising in most parts of the 2,400-square-mile county, areas at higher elevations were experiencing larger increases. Properties located 2-4 meters above sea level rose 11.5x in value on average over the 1971-2017 study period, while those located at or within one meter of sea level rose 8x on average. Current climate projections of Florida’s coastline in a warming world show that areas less than a foot above sea level will be underwater within another 50 years.
The Harvard study put the concept of climate gentrification in the public eye for the first time, but we can see examples of it just about everywhere. “In California, wildfires are becoming more common and forcing people to move, in some cases because their homes were destroyed, and in others because the threat of fire makes it difficult to get insurance or a mortgage,” reports Aparna Nathan of Harvard’s Science in The News blog. “Los Angeles, in particular, may see an influx of people from the coast (as sea levels rise) and further inland (as fires rage) into its traditionally working-class Eastside neighborhoods.”
Another area where climate gentrification has become a problem is Arizona, where people are moving from the overheated Phoenix area to the cooler, higher elevation areas of northern Arizona. According to Nathan, this trend is disrupting communities and the real estate market, and widening socioeconomic gaps in the process. Jesse Keenan, lead author on the Harvard study, concurs, telling Bloomberg News that the situation in Miami “evokes matters of equity and justice that have very limited historical precedent.”
Now that the issue is coming to the fore, environmental justice advocates hope that municipal planners and government officials start taking climate gentrification into account when developing master plans and drafting new zoning ordinances to make sure that even poor people have safe places to live in the face of increasing environmental torment. But as Nathan points outs, housing is just one example of an overarching theme: “as the climate changes, it will be easier for those with more resources to adapt.”
Dear EarthTalk: Is the profusion of lawn chemicals causing the rise in dog cancer rates, and if so, how can I protect my dog?
—Bill W., Ithaca, NY
Maybe you shouldn’t let your dog run free at the park or in your neighbor’s yard if carcinogenic chemicals are in the lawn. Credit: Brett Sayles, Pexels.
Unfortunately, the answer may very well be yes. A 2012 study published in the peer-reviewed scientific journal, Environmental Research, found that exposure to certain lawn care products, such as the nearly ubiquitous herbicide 2,4-Dichlorophenoxyacetic acid (2 4-D for short), increases dogs’ chances of developing Canine Malignant Lymphoma (CML) by 70 percent. When ingested repeatedly, 2 4-D acts as an endocrine disruptor, mutating a dog’s white blood cell count allowing malignant tumor cells to replicate unchecked. While obviously worrisome for dogs and those of us who love them, the implications for people aren’t good either, given the similarities between the onset of CML in canines and non-Hodgkin’s lymphoma in humans.
A 2013 study in another peer-reviewed journal, Science of the Total Environment, found that “exposure to herbicide-treated lawns has been associated with significantly higher bladder cancer risk in dogs.” Certain breeds of dogs (terriers, beagles, sheep dogs) are at greater risk, but needless to say lots of 2 4-D or other synthetic lawn chemicals like glyphosate (the active ingredient in RoundUp) aren’t good for dogs of any stripe. “A strong justification for the work was that dogs may serve as sentinels for potentially harmful environmental exposures in humans,” report the researchers behind the bladder cancer study.
What can you do to help prevent more dogs (and humans) from getting sick? For starters, avoid using lawn care chemicals around your home. And if you hire or manage someone else to take care of your yard, make sure they are not using 2 4-D, glyphosate or any other potentially hazardous pesticides, herbicides or fertilizers. Getting rid of your lawn altogether and replacing it with regionally adapted native plants that don’t need fertilizers or pesticides to thrive is another way to protect dogs from chemicals while saving yourself the trouble of having to mow the lawn.
If you can’t live without a grassy green lawn and can’t bear to just let it go wild, opt for all-natural, organic inputs. For instance, organic compost distributed across your lawn with a shovel in a thin layer can do just as well or better at nourishing your grass as chemical fertilizers. For weed control (beyond good-old hand-pulling), a great all-natural alternative to RoundUp is BurnOut, which uses the power of food-grade vinegar and clove oil instead of glyphosate to eradicate unwanted plants.
As for protecting your dog while out on a walk, steer clear of private lawns, even if you have to leash Fido to keep him out of neighbors’ yards. And the days of letting your dog run free in parks where your municipality may use questionable landscaping chemicals are over now that we know the potential consequences. Fortunately, many enlightened cities and towns have taken steps to rid their publicly accessible lands of such hazardous treatments. But you won’t know unless you ask, so contact your local parks department to find out exactly what they’re spraying. And if you don’t like the answer, rally other dog owners to help get it changed, for dogs’ sake.
PUDDLES 
I was told by a solar company that I did not qualify because of the pitch of my garage roof. I am very much interested in solar energy for my home. That company suggested ground panels but said it would take up 1/3 of my tiny yard. What are my other options?