Party Walls

Why Commission Solar Photovoltaic (PV) Systems?

Falling costs and rising demand for clean energy have increased the specification and installation of solar photovoltaic (PV) systems worldwide. In NYC, Local Laws 92 and 94 require solar PV and/or green roofs on all new buildings and alterations where the existing roof deck is being replaced. Third-party commissioning increases the likelihood that a PV system will perform as designed throughout its lifetime and reduces poorly performing PV systems, which erode the bottom line and damage solar energy’s reputation. This is probably why the NYC Energy Conservation Code requires that renewable energy systems greater than 25 kW be commissioned (C408.2).

Many factors can affect a PV system’s power output. Let’s look at some reasons why output may be less than expected.

Design Flaws

Commissioning agents help prevent design flaws when brought onto the project early in the process. Here are a few common design flaws:

Electrical Issues: In traditional string systems, modules are wired in series to increase voltage, as shown. However, if too few or too many modules are wired in series, the voltage will be outside of an inverter’s input range and there will simply be no power output. If modules of dissimilar current are wired together output will be reduced since the current of a string is limited by the module with the lowest current.


Building Energy Performance Standards (BEPS) are Coming to D.C., Are You Ready?

In January of this year, the Clean Energy DC Omnibus Amendment Act of 2018 was signed into law, establishing minimum Building Energy Performance Standards (BEPS) for existing buildings. The law requires all private buildings over 50,000 square feet to benchmark energy use and demonstrate energy performance above a median baseline beginning January 1, 2021. If a building does not score above the median performance, it has five years to demonstrate improvement or face financial penalties.

While quite a few of the details on enforcement are still being worked out, the median scores will be based on 2019 building performance and there are actions you can take today to get ready for BEPS.


Recent Developments in Off-Shore Wind Energy Production and Renewable Energy Storage

Image of off shore windmills

Block Island Wind Farm, courtesy of the US Department of Energy


There have been several local and global developments recently with regards to off-shore wind turbines. Advancements in energy storage from both wind and solar energy, coupled with the increased rate of adoption of wind turbines could serve as a major step towards a more renewable-based energy grid and a more sustainable future.

Updates on Energy Production

First, let’s explore some recent news surrounding the adoption of off-shore wind turbines. On a global scale, Scotland’s Hywind project recently proved that technology developed for and by the oil drilling industry can be successfully applied to off-shore wind turbines.[2] The floating 30 MW wind farm, made up of five turbines off the Aberdeenshire coast, has been operational since October 2017. During a three-month period of stormy conditions from November 2018 to January 2019, the wind farm managed to continue energy production at 65% of their maximum capacity. Note that during this period, a North Atlantic hurricane produced swells up to 27 feet! Over the course of a year  “maximum capacity” is approximately 135 GWh of electricity- or enough to power 20,000 Scottish homes. To ensure that the turbines can withstand weather events on that scale, the floating turbines are ballasted by 5,000 tons of iron ore, and 1,323 tons of chain anchor it to the seafloor. This off-shore farm proves that wind turbines can be successfully deployed in deeper waters where it would be increasingly expensive to extend the physical structure of the turbine tower to the seafloor. Additionally, the US, UK, Ireland, Portugal, Spain, France, and South Korea all have started to piggyback off the success of the Hywind farm in various ways. For instance, South Korea partnered with the Equinor, the primary backer of Hywind, to conduct a feasibility study for a 200 MW farm that would be located off the coast of Ulsan.[3][4][5][6]


Improving the Efficiency of Your Single-Family Home

Buying a home can be overwhelming. There are many factors that need to be considered and decisions that need to be made. For many Americans, aesthetics often outweigh certain characteristics critical to a home’s success, such as health, comfort, and efficiency.

To help us evaluate these critical characteristics, we’ve asked SWA’s COO and Mechanical Engineer, Srikanth Puttagunta, to walk us through his recent home-buying experience. Sri discusses ways to maximize a home’s value by taking advantage of incentives, enhancing existing infrastructure, and making the key decisions that may benefit your family’s health and comfort for years come. Join us as we dive into the essentials of single-family home ownership.  (more…)

Solar PV – The Revolution Continues

By the end of 2050, solar energy is projected to be the world’s largest source of electricity. While utility-scale solar will comprise much of this capacity, there will also be significant growth in the commercial and residential sectors – particularly in cities.

On episode three of Buildings and Beyond, Kelly interviews SWA’s solar expert, Eric Wallace, to discuss the various factors affecting solar photovoltaic (PV) growth including changes in technology, policy, and financing. Tune in to learn about some of the barriers and opportunities that solar developers face in the height of a solar revolution.  (more…)

Trying to Be Rational in an Irrational World

Think about the last time you went looking for a new car. What did you look for? I am guessing you started with your needs for a vehicle. Are you looking for a large car/SUV to move a lot of people or equipment, a car for commuting to work, or something to enjoy on the weekends? Next you probably were interested in the looks of the vehicle because it is a large investment and you should like what you drive. I am guessing you glanced at the miles per gallon (mpg) of the car. You even likely went online to see reviews from others on the comfort, crash test rating, and typical maintenance issues of the car. Of course, you will need to look at the sticker price. I am even assuming you asked to test drive the vehicle to make sure that the information that you obtained aligns with how you perceive the vehicle.

Image of animated home Now, what if I told you that you must make that vehicle purchase decision only based on the dimensions of the car, the features (radio, A/C, seat controls, etc.) of the car, some pictures of the interior, and the price. Do you think you could decide on which car you would want? My guess is that you would say I am crazy and that you wouldn’t make the decision on such a pricey purchase with so little information. But, that is exactly what millions of people do when making a significantly more expensive purchase… a home.


Designing Solar for High Density Areas

As seen in:

Humans have been trying to harness the power of the sun for millennia. The advent and popularization of photovoltaics in the latter half of the twentieth century made doing so accessible to the masses. Today, solar arrays are commonly seen adorning the roofs of suburban homes and “big-box” retailers, as well as on other landscapes including expansive solar farms and capped landfills. Until recently, the common thread amongst these locations has been the employment of open space. Solar applications have historically been reserved for use in areas of low-to-moderate building density.

By the end of 2050, solar energy is projected to be the world’s largest source of electricity. While utility-scale solar will comprise the majority of this capacity, there will also be significant growth in the commercial and residential sectors – particularly in cities. Industry influencers are increasingly focused on creating opportunities for solar applications in high-density areas, where much of the demand lies.

In their 2014 Technological Roadmaps for solar PV and solar thermal electricity (STE), the International Energy Agency (IEA) predicts Solar PV and STE to represent over 25% of global electricity generation by 2050In their 2014 Technological Roadmaps for solar PV and solar thermal electricity (STE), the International Energy Agency (IEA) predicts Solar PV and STE to represent over 25% of global electricity generation by 2050.



Nanogrids: A Whole Building Approach to Distributed Energy Resources

Distributed Energy Resources

Distributed Energy Resources (DERs) are a growing part of the energy landscape in the United States, and they are becoming an ever more attractive opportunity for households, companies, and building owners to gain control of their own energy needs. By 2024, it is estimated that solar PV plus energy storage will represent a $14 billion industry [1]. These resources are installed on the customer side of the utility meter and include distributed generation, such as combined heat and power (CHP) and solar photovoltaics (PV); energy storage assets, such as batteries; energy efficiency and demand management; and building energy management software. When deployed correctly, DERs have the potential to reduce the carbon footprint of the electric grid, increase grid reliability and resiliency, and defer the need for costly upgrades to grid distribution and transmission infrastructure [3,4,7]. (more…)

Solar Photovoltaics and New York Energy Code

Industry Trends

Over the past decade, the story of solar photovoltaic (PV) power has been one of both accelerating deployment and consistent, significant reductions in cost. This success has been driven by increasingly advantageous economies of scale, and supported by incentives and initiatives at all levels of government.

Figure 1. Solar PV systems have seen a dramatic reduction in cost

In late 2015, the federal Investment Tax Credit [3], a primary financial incentive for solar PV systems, was extended at its current rate of 30% through 2019, despite a contentious environment in Washington. It is scheduled to be stepped down through 2022, after which the commercial credit will expire and the residential credit [7] will remain at 10% indefinitely.

The National Renewable Energy Laboratory’s annual solar benchmarking report [4] shows that over the past seven years, PV system costs have dropped 58.5% in the residential sector, 59.3% in the commercial sector, and 68.2% in the utility-scale sector. As a clear sign of the times, utility-scale solar achieved the U.S. Department of Energy (DOE) SunShot Initiative’s goal of $1.00/W early this year, three years ahead of schedule [9]. According to the U.S. Energy Information Agency (EIA) [8], these trends should continue, leading to solar power’s increasing presence as a key component of the national electrical generation mix. The EIA projects solar to be the fastest growing form of renewable energy, increasing by 44% by the end of 2018 for a total deployed capacity of 31 GW and accounting for 1.4% of utility-scale electricity generation.


Five Year Solar Performance on Connecticut Home

Written by Gayathri Vijayakumar, VP – Senior Building Systems Engineer

Over the last 10 years, we’ve seen great strides in the solar PV market in the United States. Between the federal tax credit and utility-sponsored incentives, the price to install PV systems came within reach of many homeowners. For others, eager to make a positive impact on the environment, power purchase agreements with solar companies and no up-front costs made it possible to utilize their roofs to generate electricity.

While the calculated cost-effectiveness of solar panels relies on the future price of electricity (which we can’t predict), we can confirm that they do deliver energy. In a very scientific study of exactly one home, owned by a SWA engineer, five years of generation data is available. Sure, it’s not the pretty Tesla roof, but these panels were installed back in November 2011. At 4.14 kW, with no shading and great Southern exposure, the panels were estimated to generate 5,400 kWh/year of electricity in New Haven, Connecticut (Climate Zone 5). The panels have exceeded expectations, generating on average, 6,200 kWh/year, which is roughly 70-80% of the electricity required by the 2,500 ft2 gas-heated home and its 4 occupants.