Solar Energy Solar Panel Washington DC Solar
Written by Roger Perry

Practical Considerations for a Battery System

As long as I’ve been doing solar, people have been asking about batteries. The response has always been “yes, we can do them, but it will cost a lot”. That usually ended the conversation.

One question to ask is “why do you want batteries?” Do you lose power frequently? If not, a portable generator will keep your refrigerator, freezer, computers, tv and some lights going. Downsides are; noise, fumes, refueling, having to run extension cords to where needed and putting everything away when power comes back. Not too bad once in a while and it’s very cost effective. Just hope you aren’t out of town when power goes out. There is nothing automatic about this set-up.

If you lose power often and don’t want to do the portable generator dance every few months, you can get a permanently installed generator with automatic start. These are close to $5000 installed for the ones that will run most of your house when the power goes out (a larger one can be installed for a few thousand more that will run everything). This is what hospitals and critical buildings use. Power goes out, the generator starts automatically and powers the house with only a momentary loss of electricity.

Downsides? Noisy, they need maintenance and, if propane or diesel powered, they need the fuel tanks to be kept filled.

What if you lose power often, don’t want the noise, maintenance and fuel expense of a generator? What if you want a system that is environmentally friendly, will turn on automatically, is silent, will run pretty much nonstop without refueling? You should look into installing a battery back-up system connected with a solar system.

What are the downsides? Well, cost is one. While not as expensive as in years past, battery back-up systems are still costly. Compared to a permanently installed generator, battery backups tend to run few thousand more. Ask your accountant but you may be able to take the 30% solar tax credit on the additional cost of the batteries. This brings the price in line with a generator.

Another downside is you can’t run everything in your house. Things a battery cannot run for any length of time are air conditioners or heat pumps, electric water heaters, electric dryer or electric ranges. What they can run are gas or solar water heaters, gas or oil boilers, refrigerators, freezers, lights, tvs, computers, fans and pretty much everything else. Well pumps are on the edge depending on how efficient they are. While running a modern variable speed well pump is not an issue, older well pumps require a large startup current which can be too much for the battery to handle. We are about to install a “soft start” control to try and reduce a well pumps surge demand for one of our customers but the jury is still out.

We are now installing LG Chem lithium Ion batteries. LI batteries have a lot of advantages over the old lead acid batteries. The big advantage they have is they are not damaged by running them dead, whereas lead acid batteries do not like being discharged to less than 50% of charge, a Lithium Ion battery will give you it’s full rating. The one we use is rated for 10 Kilowatthour (KWH). A lead acid battery would need to be rated at 20 KHW to achieve the same capacity. Lithium batteries are also much lighter (not that the customer will have to move them) and can be charged much faster.

The big downsize of LI batteries is the upfront cost compared to LA but they will last much, much longer and they are maintenance free.

In a future blog I will discuss the two different ways to interface a solar system with the batteries, AC coupled and DC coupled and the pros and cons of each as well as what a 10 KWH battery will give you as far as run times for various appliances. I’ll also talk about how a battery system can be retrofitted to your existing solar system.

Written by Lisa Walsh

Supercharge your Solar Water Heater

Solar Thermal not Solar PV: When talking about solar and space heating, it’s worth mentioning that the panels used for this type of solar application are not the same panels that power a house, a light, or any other electrically powered appliance. In fact, the only similarity between a PV (photovoltaic/electric) solar panel and a Thermal Solar Panel is that they both absorb solar energy. However, how each panels processes and distributes that energy is entirely different.

Enlarged Domestic Hot Water System: In order to make a solar space heating system cost-effective, most space heating systems are designed to include the home’s domestic hot water supply – thereby offsetting the gas/oil/electric bill and returning the solar system’s investment. Therefore, any space heating system is basically an enlarged solar water heating system. These systems that combine solar water heating and space heating are often referred to as combisystems. This combination is achieved with a solar storage tank that comes equipped with two separate heat exchangers; one for the domestic hot water loop and one for the space heating loop. The cooler water returning from the heating system passes through the upper heat exchanger on it’s way back to the boiler where it does one of two things: It picks up some heat that was generated by the solar system or, if the tank is cooler than the returning water, acts as a buffer tank allowing the boiler to have fewer on / off cycles thereby making it more efficient.

Space Heating Infrastructure: Radiant floor heating systems are highly compatible with solar thermal energy. This is mainly because these systems are designed to operate at low temperatures and thus the solar system can contribute energy more of the time. Hot water baseboards, radiators and other hydronic heaters can also benefit, especially if an outdoor reset control is installed. The outdoor reset control adjusts the boiler’s target temperature according to the outdoor temperature.
Forced air systems can also be modified to accommodate solar by placing a fan coil inside the existing duct work. A controller senses when the fan needs to be activated and, again, a conventional back up system kicks on as needed.

Heat Dissipation in the Summer: Of course here in Maryland/Washington DC,  in our Mid-Atlantic climate, solar energy for space heating is being summoned at a time of year when insolation (sunshine) levels are much lower than the rest of the year. Therefore more solar panels are required to meet the quota. A family of four would realistically need two, 4′ x 8′ flat plate collectors for their home’s hot water supply. Depending on the required space heating square footage, this collector size may be increased anywhere between 30 – 100%. To avoid overheating in the summertime when space heating is no longer required, there needs to be a mechanism to dispose of the excess heat. This can usually be achieved with anti-stagnation functions on the controller or by installing a heat dissipater on the roof. An ideal situation is to redirect this excess heat to a pool or hot tub, thereby creating a year round triple-application system that provides the largest return on investment.

Washington DC Solar Commercial Solar Service
Written by Rick Peters

Commercial Solar Water Heating: ANOTHER Renaissance?

Washington DC Solar ,Commercial Solar ServiceSolar water heating has quite a long history. In the United States alone, the industry has boomed and busted 3 times in the last 130 years – each time displaced by cheap energy. Many are surprised to know that the first US patent for a residential solar water heater was issued in 1891 to Clarence Kemp, a Baltimore inventor. That’s right, 1891.  In the 1920’s, 30% of the homes in Pasadena, CA had solar water heaters.  With the discovery of natural gas resources in the region, the industry evaporated almost overnight.  Solar thermal technology is mature and efficient; the problem lies with allowing our commitment to solar to dissolve in favor of decreasing natural gas prices.

In these previous industry “busts”, energy became cheap and we were lulled into a false expectation of stable prices. Each time, not long after the industry was dismantled, energy prices began to creep back up, making us long for that clean and cheap solar energy again. So today Solar Water Heating is on the rise again. Will it be different in the 21st century or are we doomed to repeat the same cycle? What was it that Winston Churchill said about failing to learn from history….?

The recent surge in US solar water heating deployments began in 2008. This resurgence, especially at the commercial scale, has helped to drive up adoption rates while scaling down installation costs. Several factors are converging in recent years to bring about this renaissance:

  • Engineers, architects, and contractors are becoming increasingly familiar with this mature technology – improving costs with increasing experience
  • Regional incentives are bolstering the existing federal incentives to reduce the capital investment.
  • The federal government has mandated that a minimum of 30% of water heating must come from solar for new construction or major renovations on federal buildings.
  • Project Developers like Skyline Innovations (http://www.nextility.com/) have introduced new business models to help deploy these systems for those without available capital.
  • Property owners increasingly want to have more control over their energy budget
  • Various societal pressures continue to reward solar adoption
  • An improving economy has allowed property owners finally to reinvest in their buildings

Remarkably, much of this has occurred despite a backdrop of rapidly falling natural gas prices (the primary heating fuel for commercial water heating), decreasing drastically from 2008 to 2012. However, in the last 18 months, natural gas prices are climbing again in a trend that is likely to continue: gas exportation; deployment of energy intensive manufacturing in the US; diversion of more natural gas to transportation (locomotives, trucks, fleet vehicles and eventually automobiles); conversion of more power plants and residential heating to natural gas.In light of these trends, property owners are rapidly moving forward to install solar water heating systems before the financial incentives expire. Business owners with substantial hot water loads in Washington DC and Maryland are able to achieve simple ROIs of 2-7 years. This approach requires them to take a slightly longer perspective, recognizing that they are buying 30+ years of energy up front for a fixed price (with generous subsidies). Whether financed independently or through the bank, building owners are able to lock in their energy prices and hedge the inevitable increase in fuel costs while leveraging all of the other benefits of renewable energy.

If you have any doubts about this trend, visit our commercial solar water heating page and take a look at the photos of just a subset of the projects we’ve been deploying in the region (https://solarsaves.net/commercial-solar-water-heating/).

If you want to know more about the history of solar water heating, check out this excellent book: The Golden Thread: 2500 Years of Solar Architecture and Technology, coauthored by Ken Butti and John Perlin.

Written by Anonymous

Frederick County Detention Center to get Solar Heating

COUNTY DETENTION CENTER TO GET SOLAR HEATING

The Frederick County Adult Detention Center is going green as work has begun on the installation of a solar power array that officials hope will save the county money in the long run.

The roof-mounted system will be used to heat water for the jail, which Lt. Keith Welty, commander of fiscal services, said is one of the counties largest users of hot water…

Written by Anonymous

Baltimore Business Thermal SRECs

Maryland Solar Water Heating Bill Moves Forward

The House of Delegates voted 132-5 Saturday, following the Senate’s unanimous 47-0 vote March 17.

The legislation would allow owners of solar water-heating systems to sell renewable energy credits. The credits are bought by utilities and power companies that need to meet government quotas of renewable energy generation; if they can’t generate enough green power on their own, they can buy credits from someone else who has.

The ability to generate credits via solar water heating makes those systems a more attractive investment and rewards the buyers for using less fossil fuel. That is expected to be a boon for the green power industry, seen as a growing source of new jobs.

Gov. Martin O’Malley pitched the legislation along with dozens of lawmakers as co-sponsors. House and Senate versions of the bill still must be passed by the opposite chamber, which is expected since the two bills are identical. O’Malley is then expected to sign off.