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This is the fourth in a series of posts written by Free Hot Water’s co-founder and senior mechanical engineer, Gal Moyal. We’ll be posting this series every Wednesday, so please make it a date. Some of the information may be very technical, but if you have any questions at all, please feel free to contact us. We sincerely want to help. If you would like to have a more hands-on experience, explore our certified Free Hot Water training courses. –Solar Fred.
Collector Efficiency
Now that we’re more familiar with the two main heat collection methods available, one may ask how we decide when to use one over the other? The answer is collector efficiency.
The first step in designing active solar energy systems is to pick a system that will maximize energy extraction over a wide range of operating conditions.
One method is to compute the thermal efficiency of a collector, which is the ratio of the average heat output from the collector divided by the rate that solar radiation strikes the panel.
The thermal efficiency of a collector is calculated by using the formula bellow:
P= [(Ti – Ta) / I]
P= Inlet Fluid Parameter
Ti= Inlet fluid temperature to the collector (ÂşF)
Ta = Ambient air temperature surrounding the collector (ÂşF)
I = solar radiation intensity striking the collector (Btu/hr/ft2).
The greater the delta value in fluid temperature of the inlet fluid Vs ambient, the harder the collector needs to “work.”
(Click to Enlarge)
For example, a flat collector that has the efficiency characteristics of above line that receives water that has temperature of 55° F and the ambient temperature is 75° F with a radiation intensity of 110 Btu/Hr/Sqft (see above NASA link for your respective area) would compute as follow:
P=[(55-75)/110] = 0.18
Looking up 0.18 at the above graph would show that a flat collector would work best for that kind of environment.
Today is the 40th anniversary of Earth Day. It’s also the day that Free Hot Water publicly revealed that it was part of 17 solar companies and solar professionals offering free solar to the White House.
Here’s the official press release that includes all of the participants.
Here’s a Facebook page that you can sign up on to show your support.
Why is this initiative so important? Why should you care? Because solar needs public champions and symbols more than ever. If you turn on the radio or watch t.v., you’ll see green-washed oil, gas and coal companies spending millions of dollars to tell you that they’re not so bad, that their pollution of our water and environment is just the cost of doing business and providing energy.
Companies like Free Hot Water don’t have multimillion dollar advertising machines to tell consumers that solar hot water is reliable and affordable now. Not only that, it’s safe for workers and it doesn’t damage the air or the water that the sun heats.
That’s why instead of a huge expensive advertising campaigns, solar companies need large public symbols of solar. Having solar hot water and solar PV on the White House is that large public symbol. It says that America is once again and permanently committed to clean energy. (Jimmy Carter had solar hot water panels on the White House, but they were later removed after he left office.)
So far the White House has not responded to our offer, but you can help. Please take the time to join the facebook page. There is also a petition site started by one of the other contributors, Sungevity. We have a goal of raising 10,000 signatures and FB fans.
Add your voice. Tell your friends. Share this post on Face Book. Tweet about it. Get the word out and tell the White House to accept our collective offer and this symbol of energy independence for our nation.
This is the third in a series of posts written by Free Hot Water’s co-founder and senior mechanical engineer, Gal Moyal. We’ll be posting this series every Wednesday, so please make it a date. Some of the information in future posts may be very technical, but if you have any questions at all, please feel free to contact us. We sincerely want to help. If you would like to have a more hands-on experience, explore our certified Free Hot Water training courses. –Solar Fred.
EVACUATED TUBE COLLECTORS:
Evacuated Tube Collectors consists of several glass tubes, each of which has concentric inner and outer walls. The inner space is evacuated and the vacuum helps keep the inner tube isolated.
The system works on the same principal as a Thermos® bottle. Just like a thermos, the solar evacuated tube allows most of the heat loss to be eliminated. That makes evacuated tube design a preferred system in cold climate areas. However, you always need to pay attention to the header design. This is the weakest area of the Evacuated Tube collector design.
How it Works
The sun’s energy is trapped by the absorbing strips and transferred to a specialized fluid that is sealed within the internal copper tubing. When heated, this fluid changes from liquid to vapor and rises toward the top of the tube, and into a manifold assembly located at the top of the collector.
Heat conducts though this copper capsule into a fluid circulating along the manifold were it heats the water that flows into the manifold. Once the fluid cooled, it condenses back to a liquid and flows back to the bottom of the tube, ready to repeat the cycle.
Evacuated Tube Solar Collector (Click to Enlarge)
That’s it for this week. Next Wednesday will be much more complicated. Gal will be explaining collector efficiency and how that effects the choice of panels. Warning: There will be calculus. If you have any questions about any post, you can always contact Gal, and he’ll be happy to explain. To keep up with the latest posts, you can also join our Facebook page and start a discussion there. Thanks.
Wisc. police dog sniffs out solar savings (Photo: Flickr/Beige Alert)
Well, it’s been quite a week for solar thermal and solar hot water/solar thermal news.
Of course, we first have to mention that our very own Free Hot Water 7000 Series panel has been approved by the SRCC for 0G-1oo applications. We’re very proud of our 7000 Series and it’s potential to make save apartment buildings and hotels a lot of money on their hot water costs. Please see the details and specifications here in our press release.
In other news, Rhone Resch, the President of the Solar Energy Industries Association (SEIA), delivered the “U.S. Solar Industry Year in Review 2009″ report. Check out the full report here. In terms of solar hot water and solar thermal, 2009 was a rough year for the solar hot water pool installations due to the economy. However, it’s expected that things will improve in 2010 with the economic recovery. The report also mentions California’s goal of installing 200,000 solar water heating systems with its new incentive. If you’d like to take advantage of that incentive, by all means, please contact us for a quote or use our solar thermal cost estimator.
Police in Wisconsin catch solar hot water…for their prison. It’s criminal that more government buildings aren’t taking advantage of solar hot water savings and stimulus funds. But not for La Crosse County law enforcement. They applied for stimulus funds and were granted enough to install 32 solar hot water collectors on their Law Enforcement Center, which includes the County’s prison. The prison cafeteria, laundry, kitchen, and showers will all be able to take advantage of the solar hot water system, saving County tax payers many thousands of dollars over the next two decades. The payback will be within 10 years, says a county official. Read more.
That’s the most important solar hot water news of the week. If you want to make solar hot water news for your business or local government, please contact us for a free estimate. Thanks.
This is the second in a series of posts written by Free Hot Water’s co-founder and senior mechanical engineer, Gal Moyal. We’ll be posting this series every Wednesday, so please make it a date. Some of the information in future posts may be very technical, but if you have any questions at all, please feel free to contact us. We sincerely want to help. If you would like to have a more hands-on experience, explore our certified Free Hot Water training courses. –Solar Fred.
FLAT PLATE SOLAR COLLECTORS:
The principal component of a flat plate solar collector is the absorber plate, which consists of an assembly of a copper sheet and copper tubing.
The top surface of the absorber plate is coated with either a dark colored material or with a selective absorbent coating that is designed to extract as much as 15% more heat for the same active area. The solar radiation that strikes this surface is converted to thermal energy that’s used to heat the fluid flowing through the tubes.
To ensure extended service life, Free Hot Water collector parts are housed inside an anodized Aluminum case that’s capable of withstanding many years of exposure to the elements. The components inside and the back of this enclosure are insulated in order to minimize potential heat loss.
Anatomy of a Solar Flat Plate Collector (click for larger photo)
The upper surface of the collector is covered with tempered glass with low iron oxide content. The glass is designed to withstand high thermal stress (heat from the sun!) as well as impact from hailstones.
Free Hot Water’s Flat Plate Solar Collectors are high performance thermal collectors certified by the Solar Rating and Certification Corporation (SRCC) as OG-100, appropriate for large installations such as apartment buildings, hospitals,restaurants, retirement homes, and other businesses.
That’s it for this Wednesday. Return next Wednesday, when Gal will continue Solar Thermal 101 with a description of Evacuated Tube Solar Collectors. If you have any questions and want to skip ahead, please contact us.
Photo: Flickr:/SteveCadman Solar Hot Water Apartment Building
Solar thermal systems have been around for over 100 years and remained a cost effective alternative to gas and electric bills around the world…. except the U.S. The bust and boom of solar incentives in the 1980′s decimated the U.S. solar hot water industry, but after 30 years, solar incentives are back…. at least for now.
Recently, a number of states have implemented solar hot water incentives for businesses, such as hotels, apartment buildings, restaurants, laundry mats, car washes, etc. Each state has its own policy and every business has different needs, so the net costs will vary. Use our solar thermal cost estimator to find out your costs, or check out a sample of commercial solar thermal rebates in these states, below.
Arizona: Commercial buildings are eligible for a 10% tax credit of up to $25,000 for one building, or an aggregate of $50,000 per customer in one year. The Phoenix based APS provides a performance based rebate, which can range between $0.051/kWh-equivalent and $0.07/kWh-equivalent, up to 50% of total system cost. Other utilities in Arizona have their solar water heating incentives, as well.
California: Natural gas heated commercial or multifamily buildings up to $500,000 towards the cost of a solar thermal system.
Hawaii: State rebates for commercial installations add up to $125 per deferred kW, plus $0.05/kWh for retrofits. In addition, businesses can receive a state tax credit of 35% of the actual cost or $250,000, whichever is less. Hawaii businesses also get a 100% real estate tax assessment exemption for the new solar hot water system. Your business may also qualify for specific utility rebates as well, such as Kaua’i Island Utility Cooperative (KIUC) which pays for 50% to 80% of equipment costs.
Florida: In Florida, commercial buildings and apartment buildings receive 15 per 1,000 BTU/day for solar hot water installations, up to $5,000. In addition, Florida has long exempt any sales tax for solar thermal systems.
Texas: Businesses get a 10% corporate tax deduction based on amortized cost. All Texan companies are also free of any property tax assessment from the new solar hot water equipment. In addition, each utility has their own rebate program.
Pennsylvania: Pennsylvania’s new Sunshine solar program provides businesses a rebate up to 25% of installed system cos, to a maximum rebate of $20,000.
Maryland: The Maryland Energy Administration (MEA) is giving mid-size commercial and industrial companies a solar hot water grant of 15% of installed cost up to $25,000. The solar thermal system must be at least 100 square feet in size. Businesses may also qualify for an additional state rebate of $2,000.
The Federal Government. Finally, in addition to all of the above, the U.S. government provides all businesses a 30% Federal Investment Tax Credit that is calculated before any state or local incentives, but subject to being taxed as income.
America is finally becoming serious about incentives for solar thermal systems for businesses. However, please keep in mind that these incentives are always subject to available funding. Sometimes utilities or states run out of rebate money due to high demand. Check with a local free hot water installer to find out what programs are currently available in your area.
This is the first in a series of posts written by Free Hot Water’s co-founder and senior mechanical engineer, Gal Moyal. We’ll be posting this series every Wednesday, so please make it a date. Some of the information in future posts may be very technical, but if you have any questions at all, please feel free to contact us. We sincerely want to help. If you would like to have a more hands-on experience, explore our certified Free Hot Water training courses. –Solar Fred.
The Main Components of a Solar Hot Water System
Solar collector panel. Mounted on your roof, the collector captures the heat from the sun and transfers it to the liquid circulating through the panel. Sometimes this liquid is water, but it can also be a special type of fluid that eventually transfers the heat to your home’s storage tank through a heat exchanger. See below.
Storage Tank. The heater storage tank is your home’s current boiler/ hot water heater. The heated water captured by the solar collector panel is stored in the tank for later use.
Heat exchanger. The heat exchanger transfers the heat energy captured by the solar collector panel to the potable water that is stored in the heater tank. In our system, the heat exchanger is external to the solar storage tank.
Expansion Tank. The expansion tank ensures that the system’s pressure does not exceed the pressure limits set by the system designer.
Control system. The control system consists of a controller and the circulating pump. The controller compares the temperature difference between the heat exchanger exit point and the solar collector’s exit point. When the collector panel’s temperature is higher than the heat exchanger’s temperature, the controller turns on the pump and circulates the liquid through the system until the temperature is equalized, and then turns the pump off.
Solar Hot Water Active System Design (click to enlarge)
If you’d like to see an animated illustration of the above image, see this page. That’s it for this week. Don’t forget to return next Wednesday for Gal’s next Solar Thermal 101 post. Gal will be writing about the anatomy of Solar Flat Plate Collectors.
According to a report by the California Center for Sustainable Energy, California businesses waste a lot of money and natural gas by not using California’s abundant sun to heat water with solar energy. What’s more, a new rebate program gives natural gas heated commercial or multifamily buildings up to $500,000 towards the cost of a solar thermal system.
So who could benefit most from this program? According to the report, here are the types of business that use the most natural gas to heat their business’ hot water needs.
Lodging, such as hotels, condos, and apartment buildings. Generally, hot water is included in rents and room rates, but that doesn’t mean owners don’t pay thousands of dollars toward every bathroom, kitchen, and shower.
Health, such as hospitals, nursing homes. Again, this is like
Restaurants, such as… well, McDonalds, The Olive Garden, and every Starbucks around the corner. Imagine cleaning those dishes and wracks from Free Hot Water from the sun.
Schools. Think about all of those cafeterias, athletic pools, and hot showers for those athletes
Colleges. Similar to the needs of a school, but also the needs of a hotel. Dorm rooms, cafeterias, and athletic facilities all use hot water, 24/7. That’s a lot of wasted gas if it could come from the sun.
Large office buildings. There are at least two bathrooms on every floor with multiple sinks to wash hands with hot water. And man, does California have a lot of office towers with (thankfully) hygienic employees.
So why aren’t more of these California businesses going solar? With the new incentive, the problem is no longer the cost. Between the 30% Federal Investment Tax Credit, as well as new California state incentives, upfront costs are paid back in savings in a very short time. So if it’s not cost, it’s awareness, and that’s where we come in.
First, use our easy-to-use calculator to get an estimate of what a solar hot water system will save you. That calculator is very informative, and yet, it’s just a calculator.
For your business to benefit from these savings, you really need to contact us for a free site assessment and find out if a solar water heating system is right for your roof and hot water needs. In sunny California, there’s a very good chance that it is.
Solar Fred loves it when utilities realize that the future is solar hot water and solar photo voltaics for homes and businesses. That’s why I’m glad to read that Valley Electric Association (VEA), a utility that straddles California and Nevada, is selling domestic solar hot water systems at face value to its residents. Read More.
Developers are also starting to realize that the future is hear now with solar hot water. Down in Orlando, Florida, many homes heat their pools and home hot water tanks through very expensive electric water heaters. Not so for this new home, which is the model of energy efficiency, including a solar thermal system. Read More.
I also love it when very old, traditional, institutions like Appleton Farms, one of the oldest continuously operating farms in the country, is saying that they can still be modern and energy efficient. As a result, they’ve applied for and received a grant from stimulus funds. Appleton will be using some of the money to install solar thermal hot water systems on the old farmstead. Good for you, Appleton. Oh, and by the way, this installation is another example that breaks the myth that you can’t install solar thermal hot water systems in cold climates like New England. Read More.
If you have any questions about solar hot water or solar thermal systems for your home or business, please contact us. You’re also welcome to use our solar calculator to give you an idea of how much a solar thermal hot water system will save you.
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