Builders of small commercial-, municipal- and small utility-scale installations are finding that mounting inverters and attending systems on skids in ‘power station’ configurations can save on labor costs, particularly in regions and projects that require union electricians.
New York City-based Solops LLC developed a 13 MW commercial array in partnership with Marina Energy, a subsidiary of South Jersey Industries. The ground-mounted photovoltaic array system consists of 44,270 modules and 20 inverters that are expected to produce nearly 16.9 GWh of electricity annually, all of which will be purchased by Berry Plastics Corp. of Phillipsburg, N.J.
‘We installed the inverters on open-platform skids, primarily to reduce labor costs,’ says Matthew West, executive vice president of Solops. ‘It is our policy to avoid integrating high-power systems in the field, if we can avoid it.’
West says the project required significant integration of high-, medium- and low-voltage equipment. In addition to saving on labor costs, he says skids enable a lot of the integration work to be done ahead of time, which makes for more effective and predictable scheduling.
‘We do as much of the prep work as possible before it lands on the site,’ says Cathy Crowder, product manager of integrated solutions for Advanced Energy. ‘When it arrives, the electricians just hook up the leads and communications equipment.’
Minnesota-based Blattner Energy finds skids useful for managing the construction and integration in regions subject to demanding regulatory oversight. The engineering, procurement and construction contractor built a 7.5 MW project in Valley Center, Calif., for developer Golden Concord Holdings Ltd. The project provides for San Diego Gas & Electric under power purchase agreements.
The Valley Center plant incorporates 300 W and 285 W Trina photovoltaic modules and skid-mounted inverters from Advanced Energy. According to Array Technologies Inc., which supplied the single-axis tracking systems, the site has 1000 V and 600 V sections, requiring different tracking system configurations in constrained areas with irregular property lines.
Chanda Lytton, manager of solar construction for Blattner Energy, says San Diego County, where the project is located, has very stringent union labor and environmental requirements that were assisted by using skidded inverters.
‘The beauty of the skid is that it saves on labor,’ Lytton says. ‘The inverters show up complete on the skids, and the workers just had to make the connections.’
On the environmental side, she says they were able to satisfy an oil separation requirement with a containment area that is built into the skid.
‘Union labor or not, if you've got the right project, you can make up for the costs of the skids,’ says Darren Bronen, manager of utility business development at Advanced Energy. ‘Plus, you should get better quality if you can perform the integration work in a controlled setting.’