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Electricity, JPS and going solar

Published:Monday | June 2, 2014 | 12:00 AM

Gregory O. Gauntlett, Guest Columnist

I refer to your article by Alessandro Boyd titled, 'Sandra gets new leaf on light: cuts JPS bill from more than $30,000 to $124', published on Thursday, May 29, 2014 in The Gleaner and wish to highlight some concerns and to explain Sandra's bill to your readers.

Going solar means reducing your dependency on the Jamaica Public Service Company (JPS) for supplying your electricity needs. For a small country like ours, large-scale departure from the grid will impact on both JPS and the remaining customers - those who can't afford solar.

Solar equipment like inverters, charge controllers, etc., are made up of electrical components (resistors, transistors, ICs, diodes, etc.) that can fail at any given point. We, therefore, must have a contingency to deal with such catastrophic failures.

Installing a second system as back-up is definitely not a viable option, and using a standby generator is too costly. We, therefore, must return to the grid at this point, and we do expect JPS to have the capacity available to supply us on demand. In order for the light and power company to do this, it must continue to maintain and invest in current and future assets. Suggesting solar installations and not wanting to have anything to do with JPS is definitely not recommended.

It stands to reason that if more and more customers leave the grid, the utility company would see a reduction in its sales and net income, translating in a higher cost per kilowatt hour for its remaining customers - those who can't afford to install solar.

Cloud cover

Because solar power is driven by sunlight, intermittent cloud cover will interrupt the expected output on grid-interactive photovoltaic systems and makes it more difficult to manage the balancing of loads to generation. For this reason, only a specified amount of solar grid-tied systems can be allowed to feed in excess power to the grid in its current configuration.

In order to entertain more customers with feed-in arrangements, the JPS would need to invest in smart-grid technology. Essentially, this would allow the utility company to remotely control the output level of your grid-interactive inverter to aid in load balancing. Of course, the inverters must be smart-grid ready. The conversion to smart-grid will require large capital investment. In some countries, feeding back excess power on to the grid is simply not allowed.

Sandra's bill explained:

Sandra has a SunGrow grid-tie inverter that's connected directly to the JPS grid. The system is battery-less (no storage) and generates electricity during sun hours only. The new digital metre has two accumulators that record the amount of kilowatt delivered and sold.

Her system is capable of generating more than enough power to supply her home and with excess unused power to sell back to the grid. The $4,228.53 on her bill represents the cost of the electricity consumed during the nights when there is no sunshine, while the $4,418.58 deducted is the amount Sandra gets for the excess power sold to the grid. This trade-off between the quantities purchased and the quantities delivered is referred to as 'net billing'.

Sandra's daily production and savings will increase as the days get longer towards equinox.

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