Saving costs with large-scale string inverter design, part 1

CPS 60kW Ground AZ

String inverters are now a staple of the commercial and industrial and small utility-scale segments, which was solely the domain of central inverters once upon a time. The trend started about six years ago when string inverters souped-up to 1,000 volts and developers and EPCs saw the value in chasing the higher efficiencies, multiple MPPTs and greater energy harvest rewards provided by distributed string architecture.

But two years ago, the shift to an even lower cost 1,500-volt architecture started, and the math shifted right back to central inverters because 1,500-volt three-phase string inverters weren’t available.

“A year and a half ago, string inverters were about 8 cents per watt and central plus combiners were 6 cents per watt, so that seemed cheaper,” says Ed Heacox, GM, CPS America. “Central plus combiner boxes seemed cheaper.”


But string inverters have souped-up again, and that economic story has flipped again. Instead of string vs. central, the discussion is changing to distributed string vs. “virtual centralized” string. In the Solar Builder Inverter Buyer’s Guide this year, you’ll see a bunch of string inverters in the 100 to 125 kW range, and those that aren’t rated at 1,500 volts will be soon. The cost is now closer to 5 to 6 cents per watt, with central inverters still sitting at a cost per watt similar to two years ago. That aforementioned 3 to 5 MW cap is about to be a thing of the past. CPS has its 1,500-volt product coming out in June and says it is rocketing past that 3 to 5 MW sweet spot.

“We are having regular discussions about projects 20 to 30 MW in size now when before, that was extremely rare,” says Sarah J. Ozga, product manager North America for CPS America. This could possibly go as high as 100 MW in the not-too-distant future.

Now, all costs being equal, some will still gravitate to central inverters because of operations and maintenance preferences: Lots of walking or driving all over to address each O&M issue spread across a 30 MW site, and god help you if the site was mapped incorrectly. String inverters can feel unwieldy if you’re unprepared for them.

“A lot of time O&M depends on the developer or EPC’s personal experience with inverter reliability,” Heacox says. “Those who had a lot of downtime on central, are for sure leaning to string. But those who have had great experiences don’t feel they need to change for projects larger than 5 MW. But some see that if they go down the string path, there is more interchangeability among suppliers with relatively similar products — and the engineering and workload need for swapping out string inverters is a lot easier than reengineering a 3 MW power station.”

In part 2, we will look at two different string solutions that offer the lowest cost path and meet any O&M preferences you may have. We will also dive into this in MUCH greater detail in this upcoming free webinar. Sign up here.

Utility-Scale String Design

Wed, Jun 20, 2018 2:00 PM EDT

When designing a large site one consideration is String or Central. Both have well defined benefits. Historically, the large utility-scale sites have mainly relied upon central inverters. Now a third option, the Virtual Central, is paving the way for string inverters into this space. In this webinar, we will discuss the benefits and disadvantages to both the distributed and centralized string architectures and how the design choice affects installers, developers and site owners. Sign up here.

— Solar Builder magazine

Trina Solar debuts utility-scale solution with Huawei, Sungrow, Nclave


Trina Solar Limited launched a new smart PV solution, TrinaPro, at its global headquarters in Changzhou, China, designed for utility-scale ground mounted PV systems. It is the result of Trina Solar’s full cooperation agreement with Huawei Technologies Co., LTD, Sungrow Power Supply Co., LTD, as well as its strategic cooperation agreement with Nclave Renewable S.L., respectively.

TrinaPro is the first smart PV solution with an optimized combination of Trina Solar’s solar modules, state-of-the-art solar tracker systems or floating systems, and world-class inverters. As a new value-added product, TrinaPro is characterized by premium components, optimized system integration and smart O&M interconnection.

RELATED: Module Evolution: What big-time PV improvements will boost panel efficiency?

TrinaPro includes both ground-mounted solutions and floating solutions. The ground-mounted solution features a state-of-the-art solar tracker system, which will help improve energy gain by 10%-30%. The floating solution will cover several application scenarios such as reservoirs, lakes, beaches, etc. With the optimized matching among components and “Edge Computing” algorithm integration, TrinaPro can improve system stability with higher power generation and lower BOS cost in order to reduce system LCOE.

Furthermore, with the interconnection between the “Edge Computing” algorithm and a smart O&M system on a cloud platform, TrinaPro is empowered to analyze and process data from the cloud, to optimize the system’s operational model and ensure the system runs smoothly and efficiently.

— Solar Builder magazine

Origis Energy’s 52-MW solar project in Mississippi officially up and running

Lamar county solar Origis Energy

Cooperative Energy and Origis Energy officially unveiled their joint venture 52-MW solar project in Lamar County, Miss., with elected officials and business leaders joining the two companies at a ribbon cutting. The facility began operation in December.

The 540-acre site, MS Solar 3, includes 206,000 polycrystalline solar panels which gather sunlight and transform it to energy that will power up to 11,400 homes. MS Solar 3 uses the best, most efficient solar technology available. Origis Energy built, owns and operates the facility while Hattiesburg-based Cooperative Energy has agreed to purchase all electricity the plant produces. Cooperative Energy is a not-for-profit, Member-owned generation and transmission cooperative that supplies electricity to 11 Member cooperatives that stretch from the Gulf Coast to the Tennessee line.

Cooperative Energy owns a diverse generation portfolio including coal, natural gas, nuclear and renewables. It began solar generation in 2016 with the start of five 100-kilowatt solar sites built at Members’ local headquarters. “This new, utility scale solar generator represents a giant step forward for Cooperative Energy in providing solar energy for our members,” said Jim Compton, Cooperative Energy’s president and CEO. “Not only is it one of the largest solar generation plants in Mississippi, it employs the most advanced solar technology available today.”

Solar Builder Project of the Year Utility-Scale: Lamesa Solar Facility

Origis Energy is helping to power the solar revolution with the construction of more than 100 operations worldwide. The company broke ground on the Sumrall facility in May 2017 and met its goal of production by year end.

“Solar energy benefits all stakeholders – the companies, the end users, the public and the regulators,” said Guy Vanderhaegen, Origis Energy’s CEO and president. “We firmly believe you will see more electrical utility companies seek to expand their portfolio by adding solar and partnering in projects such as this one. This area geographically benefits from an abundance of sunlight and we know it will be successful in reaching its generation goals.”

— Solar Builder magazine

IBISWorld: Post-tariff solar market fundamentals remain favorable for buyers in short term

solar panel tariff pricing

It’s been about a month since the #TrumpTariffs officially went into place, and while the long-term economic and pricing implications of the tariff remain to be seen, analysts at IBISWorld say procurement professionals shouldn’t panic since the market’s fundamentals remain favorable for buyers, at least in the short term. IBISWorld employs teams of dedicated expert analysts in the US, UK and Australia who scour economic, demographic and market data, while adding analytical insight that helps organizations of all types make better purchasing decisions. Here’s a look into their thinking.

PV panels solar tariffPanel prices will still fall

While the tariff may place upward pressure on solar energy costs, PV panel prices are already falling, so the tax’s impact will be minimized. IBISWorld estimates that the average price of solar panels has been declining at an estimated annualized rate of 3.6% during the past three years, and is forecast to continue falling at an annualized rate of 3.3% in the next three years. While some of this decline is due to the availability of cheap imports, it’s also attributed to technological improvements and more cost-effective and scaled production. Consequently, though this price forecast may change, these factors will continue to keep PV panel prices in check, even as the tariff increases costs.

Moreover, in anticipation of the January decision, foreign suppliers, particularly from China and Mexico, rushed to bring in low-cost solar equipment for US customers toward the end of 2017 to beat the tariff. According to Bloomberg, there’s about five gigawatts of solar equipment already stashed in U.S. warehouses and ports, enough to supply U.S. solar projects for the next six months. This supply glut will help mitigate the impact of the tariff through much of 2018, when the tax will be the highest.

Mitigation through better procurement strategies

Businesses looking to install solar panels will also continue to enjoy tax incentives. Currently, the IRS offers a business investment tax credit equal to 30% of the cost of solar panel installation. Congress passed an extension on these tax credits in December 2015, which makes them available for solar energy systems in operation by the end of 2019. In 2020, the credit will be reduced to 26%, and then to 22% in 2021 before dropping permanently to 10% in 2022.

Procurement professionals can also take steps to insulate themselves from potentially higher prices by carefully considering their “soft costs.” These non-hardware expenses include financing, permitting, installation, taxes, inspection and more. Despite declining solar energy hardware costs, soft costs have largely held steady, and thus account for an increasing proportion of the price of solar power.

One of the best strategies for buyers to reduce soft costs is through scale. Many of these costs do not increase significantly with scale, which means buyers can spread these expenses out with large projects. Buyers should also look for vendors that offer standardized designs. These “plug-and-play” PV panel systems are modular and easy to install, enabling buyers to minimize permitting, inspection and connection costs by utilizing a standard system across all their locations.

Procurement departments can also look to build solar energy systems in states that have taken actions to reduce soft costs. For example, Colorado’s Fair Permit Act caps the fee for commercial permits at $1,000. Five New England states, including Massachusetts, Connecticut, New Hampshire, Vermont and Rhode Island, have joined forces to form the New England Solar Cost-Reduction Partnership. The partnership aims to reduce soft costs through measures such as online permitting and expedited review processes that automatically issue permits after a specified period of time.

Armed with a supply glut of imported PV panels, tax incentives and strategies for reducing soft costs, this tariff doesn’t have to be a death knell for businesses looking to adopt solar panel systems. In particular, the 30% tax credit in operation by the end of 2019 will continue to be a strong incentive for buyers considering solar panel systems.

— Solar Builder magazine

Here’s a plan to cut solar costs to offset impact of new tariffs on panel prices


This OMCO Field Fast Racking system is one example.

The moment the tariff decision went into effect, our thought was to immediately find ways to bring system costs back in line with today’s expectations, even after accounting for this inflated module price. The Rocky Mountain Institute and 35 solar energy industry leaders apparently were way ahead of us, sending word about their commitment to develop an ultra-low-cost solar product able to operate in a variety of environments at fully installed costs as low as $0.50/Wp.

Participants at the Rocky Mountain Institute-hosted event, representing at least 15 gigawatts of solar capacity-equivalent to the capacity of 25 average-sized coal plants-identified an opportunity to reduce costs by $0.20/Wp in 2018 alone. Reducing costs at this scale would mitigate the effect of newly applied trade restrictions on solar components, keeping the solar energy industry on a maintained cost-reduction pathway.

The four-day workshop saw over 35 leading companies applying best practices in system design, supply chain, business model, finance, and market structures to the debate. Members identified a pathway to create a modular, pre-engineered and pre-assembled solar product of standardized design targeting a fully installed cost of ¢50/W and lower costs by as much as $0.20/Wp (dollars in watt peak) in 2018 alone, corresponding to about an 8%-percent reduction in the average national price of residential electricity.

Those participants include:

Workshop participants:
Abraaj Group
BayWa R.E.
BHP Billiton
Certain Solar
City of San Diego
Cypress Creek
Distributed Resource Ventures
Fir Tree Partners
Georgia Tech
Guzman Energy
Kevala Analytics
Metka EGN
National Grid
Nokomis Partners
Quest Renewables
Sierra Club, Ready for 100
Solar Energy Industries Association
Sulas Industries

In the last five years, the solar industry has realized year-over-year growth rates of 21%, attracted more than $100 billion in investment, and now employs more than 260,000 people in the U.S. as one of its fastest-growing energy sectors. Yet for solar to reach its full potential as a foundational, carbon-free energy source in the U.S. and around the world, it must compete without subsidy in wholesale markets.

“In addition to the benefit of a step-change in cost reduction, a more standard offering would be particularly effective in opening up new market segments of smaller installations, where the cost of project-by-project customization has diminishing returns,” said Thomas Koch Blank, Principal, Rocky Mountain Institute

Community-scale solar (CSS), also referred to as distribution-scale solar-installations of 1-10 MWp, cited close to load and connected to the distribution grid rather than the transmission grid-is emerging as a “sweet spot” for the build-out of solar energy development. In addition to low-cost electricity, CSS provides distributed benefits such as avoided transmission costs, reduced peak energy charges, potentially avoided capital expenditure for grid upgrades, ancillary services, and increased resilience.

Increased pre-assembly is going to have the ability to create jobs in the manufacturing sector and supply chain sector. Being able to communicate this as an integrated product offering, assembled in the U.S., that messaging is going to be important. There’s not enough emphasis on solar jobs being transferable skills for those being impacted by coal plant shutdowns. Many of these jobs have transferable skills that people can slide into pretty easily.

“By taking a whole-systems approach that leverages standardization to enable preassembly and pre-engineering, the roadmap to delivering a low-cost, easy-to-understand product offering is clear. Furthermore, regional preassembly of solar equipment and components, which get trucked to local sites for efficient installation, creates new jobs and community investment,” said Jules Kortenhorst, CEO, Rocky Mountain Institute

— Solar Builder magazine