Six year old solar power plant partially repowered with new trackers and bifacial solar modules


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By John Weaver | December 27, 2019

Per some counts, at the end of 2018, there were 690 ground mounted utility scale solar power plants totaling greater than 25GWac in commercial operation in the United States. These projects represented tens of billions of dollars of installation costs, and hundreds of millions of ongoing annual operations and maintenance work. And now, a $20 billion revenue stream is arising – upgrades of racking, inverters, and solar modules via the process of repowering these plants – that seeks to maximize the amount of electricity that can be delivered through already existing interconnection approvals.

OCI Solar power has repowered a portion of their 39.2MWac / 49.4MWdc Alamo 1 solar power plant located in Bexar County, Texas. The plant has been upgraded to Array Technologies trackers and bifacial solar modules. Existing inverters, manufactured by Kaco New Energy, concrete foundations, and balance of system gear were left in place.

The facility came online in December of 2013, and sits on 445 acres of land on the southside of San Antonio. Originally, the plant was built with 167,680 modules, 295 watts each, on 2,260 single-axis and 1,932 dual-axis trackers manufactured by ERCAM Trackers.

The OCI press release was thin on details, only giving the top level descriptions. The amount of hardware switched out, the specific Array Technologies tracker model, the bifacial module manufacturer or model, nor the new capacity factor were noted. However, it was brought up that the work took nine months to complete and that it was a “major upgrade”. As well, Jason Thompson, Construction Manager for OCI, said the new block of trackers and bifacial modules, “will be used for field testing and data-gathering”.

Mortenson Construction was the original engineering, procurement and construction (EPC) firm, with Swinerton Renewable being contracted for the recent work.

In August of 2016, the facility added 1MW/250KWh of energy storage whose main purpose is to provide fast response frequency stability.

Inverter manufacturer SMA launched its SMA Repowering department in January of 2019 where it offers engineering services to support system upgrades of this nature. Spanish company TSO recently patented drone based O&M software that supports repowering in its O&M algorithms. The older European solar market has been talking about repowering for a few years now, with 40 GW of solar power plants greater than 100kW and older than five years of age.

Recently, pv magazine USA interviewed hardware manufacturer Alencon (and we have an article coming). They specifically make a piece of hardware that allows for upgrades of this nature (no note on whether they were involved in this project) – called the “String Power Optimizers and Transmitters” (SPOT for short). It allows you to connect hardware of varying voltages to each other, easing the upgrade process. This OCI Solar project noted the original Kaco inverters stayed, which were probably rated at 600 volts. Any modern solar modules would be rated at 1,500 volts and would require custom wiring.

Alencon also offers an engineering service surrounding the repowering work that they say is fundamentally important, as repowering is a very different process than originally designing to keep costs in check.

In 2018, almost half of the utility scale solar + energy storage installations were upgrades to already existing solar plant.

OCI Solar said that they were able to do the upgrades without powering down the whole of the facility, and that due to the seeming success of this upgrade they’re now looking for new facilities to similarly redevelop.

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