Solar farm blooms despite unique challenges

| 22/06/2017 | 5 Comments
CNS Business

David March, of Entropy, stands by solar panels and inverters

(CNS Business): The commissioning of Cayman’s first-ever solar farm Tuesday, 20 June, while historic on its own, was also the result of several innovations to accommodate the island’s unique requirements and overcome associated challenges. David March, managing partner of Entropy Investment Management, which partnered with CUC on the project, cited several environmental conditions that made constructing the facility an exercise in creative thinking. “No solar farm anywhere in the world is like this one,” he said. The issues started from the ground up and the solutions came through teamwork, he explained, noting the project was designed and built by Caymanians.

“Cayman’s a rock, it’s a beautiful island but it’s a rock,” March added. “Typically in a solar farm, you drive pilings into the ground and then you mount everything on that.” Since the pilings could not be driven into the rock, the mounting system that was devised was a first for the company.

“We’ve built 450MW of solar around the world and I think this the first solar farm of this size ever done as a ballasting system because you can’t just drive a piling down there, which means we would have to literally drill holes in the rock and then cement them in, which would be too expensive.”

The ballasting involved filling up each of what he referred to as “bathtubs” with 7,200 lbs of concrete, which anchor the more than 21,000 solar panels at the facility. All together, 5,000 cubic yards of concrete was used for the tubs, which March said was “probably the most expensive thing in the solar farm”.

The tubs solved one piece of the puzzle needed to ensure the facility would be able to withstand a major hurricane. “We have a 155mph hurricane wind load requirement for permit, which means you have a very, very big ballast per foot,” he said.

However, there was still an issue concerning the angling of the panels. Even with the heavy ballast, March said, “we couldn’t get the panels at their optimum angle. So these are at 10 degrees and they are supposed to be at 18 degrees,” an angle that would result in too much wind lift.

“At 155mph if these were at the correct angle, even the feet would not be able to handle it. Essentially, they’d go airborne in a hurricane. So we had to sub-optimise the energy production in order to meet the wind requirements on that.”

To compensate for that compromise, the company had to use more panels and essentially overproduce. The plant generates 6.3MW of direct current (DC), with 5MW of alternating current (AC) going into the national power grid. By about 10am the plant is “maxed out” at 5MW, he said.

There was still another innovation necessary to ensure uninterrupted conversion to AC by inverters, which, March said, “you will never see in the Western hemisphere”.

He described the usual alignment of inverters. “Typically in a solar farm of this size you’ll have three large inverters, which are about the size of a bus, so each one is about 2MW or so. You airlift them in along with everything else. If they go down, they are going to take down one-third of your solar farm. Then you have to fly people in and equipment to repair.”

CNS Business

Richard Hew speaking at commissioning ceremony

He explained that when the builders considered the time needed to repair one of these “central inverters”, there would be a two-week down time, resulting in one-third less electricity produced.

“So the plant was designed with small inverters; there are 173 30KW inverters, rather than three 2MW inverters. So, essentially one row or part of a row is an inverter. If an inverter goes down, these are hot swappable. We have a whole bunch of them in stock.

“The monitoring station will tell you which inverter is down, somebody will come out and throw one of these things in the trunk of their car. You unbolt it, uncouple it, pull it, drop another one in. And you’re up and running in a half an hour.”

The technical term for this arrangement is a “string inverter utility scale configuration”, which is necessary for reliability and service.

Additionally, every inverter “talks to” the control system, which means they know exactly what every inverter is doing.

“And it’s really nice at that level of detail; we can tell if there’s an iguana sitting on a panel because it will affect it at that micro level. So if something gets damaged, or certain panels are much dirtier or malfunctioning, it’s easier to debug them at that point.”

Having solved these issues for the solar farm, March sees all sorts of possibilities for renewable energy in Cayman, one of which is storing the energy produced as ice, by having the chilling system use any excess electricity to freeze the water into an “ice bank”.

“Most residences either turn their air conditioner off during the day or turn it way down and they need it at night. Put solar on your rooftop, store the energy as ice and when you come home your air conditioner essentially uses the ice” to chill the water that circulates, March said, explaining that this would save a significant amount on electricity used, since air conditioners typically comprise 65% of the total energy load.

Looking at the wider region, he said that the Caribbean has “unique challenges” in energy. “I would love to see a Caribbean energy innovation centre in Cayman. It’s solar, it’s wind, it’s storage, it’s ice, it’s geothermal; each one’s a unique solution. In the case of the United States, because we are so big, we always come out with single-point solutions: Hi. I’m the solar guy, or I’m the geothermal guy, or I’m the wind guy.” But in the Caribbean, “energy innovation on the grid end needs to be looked at holistically”.

Richard Hew, president and CEO, also spoke of the importance of embracing renewable energy solutions. “We have targets in the National Energy Policy to reduce greenhouse gas emission on the island as a whole and CUC has a role to play in the electricity sector. Those targets are fairly aggressive, but they are in line with the Paris Accord. We are heading in the right direction, but we have to do a lot more.”

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Category: Alternative Energy, Local Business, Technology, Utilities

Comments (5)

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  1. Rodney Barnett IV says:

    I'm really surprised at the negative comments aimed at the above story. After reading it, I came aways with a sense of excitement at how this group of individuals, corporate managers and even government came together to make this project a reality.

    Renewable energy is the future, and if we in the Caribbean expect to move forward and provide the jobs and lifestyle that will for future generations, we will need to look toward modern forms of energy such as solar to help us stay in step. I doubt everyone on the island today can afford renewable energy to fuel their homes, and the same can be said of the future. It will be the corporate community that will provide and distribute electricity from these solar farms to the masses, or to large commercial buildings. You simply cannot put alternate energy plants on top of every home, office building or hamburger shack and have an effective energy grid.

    Congratulations to all those involved in this exciting prototype for Cayman and the Caribbean. I wish you (and all of Cayman) many years of problem free operation.

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  2. Anonymous says:

    solar should never go over bare ground.

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  3. Anonymous says:

    What a waste of space. This land could have been used for something with panels on the top.
    Money, money, money. No thought for anything else.

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    • Anonymous says:

      2.34. You are the o e who is thinking, money, money, money by suggesting ways to increase profit ie doing something in addition to the panels on top.

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  4. Lodge345 says:

    Who are the local partners?

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