Written by Lisa Walsh

Developer’s Success Story – A Solar Integrated Green Roof in NE DC

By Lisa Walsh | Commercial Solar Developer | Solar Energy Services, Inc.

For the newly-finished Taylor Street Storage facility in North East DC, a 17,500 square foot green roof with fully integrated solar panel array that showcase a value-stacked, elegant design providing both a cost-effective solution to storm-water management. All without forfeiting the solar panels that generate income via federal tax incentives and DC’s superb solar production-based financial incentives.


With over three million square feet of green roofs in Washington DC and 50MW+ of solar installations – the City is no stranger to either technology. However, the integration of both on the same roof is less common, despite the symbiotic relationship between the two offering a number of advantages.


Beds of Sedums awaiting Fall planting at Taylor Street Storage, Oct 2018.
Photo Credit – David Gorman of Lock 7 Development

Completed 133.980kW Solar-Integrated Green Roof at Taylor St NE WDC
Photo Credit – David Gorman of Lock 7 Development

Storm-water Management


Approval for a commercial building permit in Washington DC must include a storm-water management plan as defined by DC’s Department of Energy and the Environment (DOEE). For Taylor St, the Development team could have chosen between:

  1. Lost parking spaces to house costly underground containers for capturing and storing runoff
  2. Payment of ever-increasing storm-water management fees
  3. Implementation of a multi-layered Green Roof to treat 100% of the rainfall obligation with a perennial, sedum based plant surface – as per DOEE requirements.
    The green roof offered a cost-effective storm-water management solution that required no additions or demo’s to the existing structure.
    Solar Panels

Solar Panels

Most savvy developers realize that an empty roof in Washington DC is money left on the table. With the best solar financial incentives in the USA, the payback is rapid followed by years of production-based paydays. Small wonder that the development team at Taylor Street were interested if – and how – a solar array could integrate with a Green Roof. The good news is not only does the solar system seamlessly integrate with the green roof but the relationship is one of symbiosis and cost-effectiveness. Here’s why:

BALLAST. Most solar systems installed on DC’s commercial flat roof areas are ballasted. i.e. an assortment of concrete blocks, along with the weight of the solar panels and racking, is engineered to hold down the weight of the array with minimal or no penetrations to the roof membrane.
With close to 35 PSF of weight, a green roof more-than provides this ballast negating the need for concrete blocks or supplemental attachments. This is worth mentioning as the Green Roof is now a fully engineered component of the solar system bringing the question of tax credit eligibility into play. Is the Green Roof, or portion of, now eligible for the 30% Federal Tax Credit? Certainly worth conferring with a tax adviser.

A close up of the Solar System mounted into the soil on the roof.

CREATION OF A MICRO-CLIMATE: Furbish designs their perennially healthy green roofs with a wide palette of sedum species. These drought-resistant succulants require little maintenance and have varying requirements for daily sunlight – from full-sun to all-shade. Contrary to first impressions the intermittent shading and weather protection provided by the solar panels provide a micro-climate highly conducive to the plants underneath, in between and around the solar arrays.

DESIGN: Most ballasted solar systems have ample aisles between each row of solar panels insuring that each solar panel is optimized and avoiding shading from the panel row in front. Solar panels can also be tilted anywhere between 5 and 35 degrees. This is adjusted to account for shading, panel count and orientation considerations. This flexibility of design was helpful for integration the green roof. Aisle spacing, solar panel size and tilt were designed with the Green roof in mind – not only as it relates to healthy plants, but also for annual maintenance access requirements.

Established Example featuring similar product and design as Taylor Street


CHALLENGES: Solar-integrated green roofs are not as common as their singular counterparts. Fair to say this project did not come without some challenges


DOEE DESIGN STANDARDS: Department of Energy and Environment is responsible for DC’s Stormwater Management and insuring all DC buildings comply with runoff standards. The burden was on SES and Furbish to ensure that the solar arrays were not going to impede the ability of the plants to thrive and provide the necessary water retention requirements. The design and permitting side of the project insofar as panel tilt, aisle spacing and racking integration were designed in collaboration with DOEE.


INSTALLATION TIMELINES: Furbish Company are Green Roof specialist, Solar Energy Services, Inc. are solar specialists. Integrating these technologies took heightened coordination between our installation teams, mostly in terms of labor efficiency, communication and timeliness. The latter was particularly stringent as the Certificate of Occupancy, required to meet the developer’s lease requirements, was contingent upon the completion of the Green Roof which now included solar racking, wiring and panel installations. Throw in some PEPCO Permission to Install challenges related to the solar portion, and the pressure was on.


The project came with some unusual PEPCO interconnection timing challenges at the end. Ironically not related to the Green Roof aspect of the application. Nonetheless, this system is now outputting electricity like gangbusters. All’s well that’s ends well.

Written by Rick Peters

Maryland Solar – Ready to Grow Again

For many years, Maryland has been a leader in solar policy and solar deployment.  In the last 3 years, we’ve fallen behind other states, watching our robust growth give way to several years of decline.  It’s almost hard to believe, but Maryland has been losing solar jobs for more than two years after peaking at approximately 5300 in late 2016.

Policy Clouds

Why is this happening?  One of the biggest reasons is the value of the state solar production incentive, the SREC (Solar Renewable Energy Certificate).  Those of you who own solar or have considered buying solar are probably all too familiar with SREC pricing.  Because Maryland property owners adopted so much solar in the first half of the decade, we outpaced the state’s goals, depressing the value of the market-based SREC incentive.  This was a good problem for the industry to have until it became clear that our goal (25% renewables by 2025 with 2.5% solar by 2022) was clearly not aggressive enough.

The Time is Now

We are now at a time of severe urgency for the Maryland solar industry.  With installations on the decline for over two years and job losses mounting, we are losing a trained employment base and leaving federal tax benefits on the table.   The solar industry has been working with other coalition members (wind industry, environmental organizations, etc.) for a few years to try to increase the state’s Renewable Portfolio Standard (RPS), but have been hampered by the Hogan Administration’s reluctance to incentivize more renewables until the completed RPS Study Report is released.  The study was due to be released in December of 2018, but has been delayed and some fear this is intended to stall an RPS increase for another year.  We cannot wait.

Governor Hogan has gone on record with his desire to fight climate change.  He recently coauthored an OpEd in the Washington Post with Virginia’s Democratic Governor, Ralph Northam to emphasize the urgency and the need for bipartisan solutions to climate change.  It is in this bipartisan spirit that we hope to see the Hogan Administration support the Maryland General Assembly in passing the Clean Energy Jobs Act
(CEJA)(SB0516, HB1158) of 2019 that will increase our renewable energy goal to 50% and the solar portion to 14.7 %. “Click here to read more about this

No-Brainer Investment for Maryland

One of the primary arguments against increasing the RPS has to do with the impact on utility ratepayers.  The preliminary indication is that the increased renewable goals associated with the CEJA will add approximately $1.85/mo. to the average electricity bill.  While this is not insignificant, it is important to note that a 2018 Daymark study, commissioned by the Hogan Administration’s Public Service Commission, found that for every $1.00 of investment in solar, we return approximately $5.00 in economic and health benefits to the state.   Solar jobs are good jobs that pay well, representing a path to economic stability for many installers.  And best of all, solar installation jobs cannot be exported.

We need YOUR help

As a solar advocate, we ask that you commit to express your support for CEJA in the Maryland legislative session this year.  The bill has been submitted and we should have a bill number shortly.  In the meantime, please continue to advocate for more solar whenever you can and be prepared to contact your Maryland state legislators to support this important legislation when the time comes.  Stay tuned for a special email notification with the bill number, and suggested talking points in the coming weeks.

Written by John Marrah III

Buy American and Save

For the month of February SES is offering $1000 off of any solar system that includes US Manufactured Panels.  That’s right, support US manufacturing and Save!  All you have to do is reference this offer during or before your site visit.

Here’s 5 More Reasons Why:

1.    Provides Jobs

The Solar Industry’s growth and inherent job creation is no secret, we are leading the pack among every other industry nationwide. Most of these jobs are being created on the installation side, but we also need to support the rest of the value chain.

2.    American Independence Includes Energy Independence

We as Americans have pride in our nation and in our independence. By generating our energy locally, with renewable resources, and US products, we strengthen our country and our independence, both individually and collectively as Americans.

3.    Do It for The Environment

Current technologies allow manufacturers in the US to support a greener, cleaner solar manufacturing process. If we invest in American-made products, we strengthen our manufacturing base, support US jobs, while insuring  that we are doing our part to contribute to a cleaner environment for ourselves, and the generations to come. Also, by reducing the need to ship overseas, the net carbon footprint is much lower

4.    We Control Labor Standards, They Don’t

The US is a leader in fair labor and safety standards. With minimum wage and safety regulations in the workplace being upheld, you can be sure that your panels are made by people who are being supported and treated fairly in the workplace.

5.    Guaranteed Quality of Goods

The term “Made in the USA” speaks of quality, excellent craftsmanship and a superior product. With a lower cost of labor abroad, many factories rely on fabrication and assembly processes by hand. This introduces higher rates of  failure when compared to the American Standard of automated soldering and assembly. While panel quality continues to improve in the aggregate, US products remain the leaders in quality and performance.  Price tags are slightly higher for Made in USA products, but you find true value among longevity and performance.

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.