|"Silicon cells, from which solar panels are constructed, manufactured from 1 ton of silica sand can produce as much electricity as 500,000 tons of coal."|
|Solar panels (Solar Direk photo.)|
There's so much information available about photovoltaic systems, it's hard for someone considering installing a system to know where to begin. My purpose in writing on this topic is to highlight some of the information which may interest homeowners in Jamaica.
The usual components of a photovoltaic system are the solar panels, charge controller, batteries and inverter.
I’m starting with batteries, because it's not widely known that, if you are still connected to the grid, and have permission from JPS for that connection, you don’t have to have batteries. Those used in most PV systems are lead-acid, deep cycle batteries. The advantage of batteries is that they give you an uninterrupted power supply, which would be important if you have frequent power-cuts.
The disadvantage of batteries are
· that they are expensive (about Ja$40,000.00 each);
· energy is lost in charging and discharging them, making the system less efficient;
· there are more components to install;
· as they near full charge, hydrogen is produced and vented out of the system. Hydrogen is a highly explosive gas, so they should be in a well-ventilated area, free from naked lights;
· they require regular maintenance and have to be refilled with ionized water;
The charge controller controls the current going to the batteries from the panels. It works as a voltage regulator and prevents the batteries from being overcharged or over discharged, which would shorten the life of the batteries.
Grid tie system
You can have a grid tie system with or without battery back-up. Even with battery back-up, there are advantages to this system. It is not necessary to install a PV system to supply the maximum load – the shortfall can be supplied from the grid. For example, you may use your a/c units only in the summer months, at which time the fridges are working harder and fans may also be in use. Thus your maximum load is in the summer. For the rest of the year, the load is less. To supply the maximum load without grid tie would mean more solar panels, and higher cost.
If you plan to install a grid tie system, you should first get permission from JPS. If you have an analogue meter, when you connect your PV system to the grid, during the day when the panels are generating excess current, your meter will spin backwards and in the night it will reverse as it draws current from the grid. If you connect to a digital meter, it will spin forwards all the time, even when you are sending current to the grid, so you would be charged for the electricity you have supplied to JPS! So that isn’t an option. Either way, JPS would prefer that customers apply for Net Billing, before system is installed.
To apply for Net Billing
1. Complete the application form in duplicate and submit one to JPS and the other to OUR (with non-refundable fee of Ja$2,000.00). Keep a photocopy for yourself.)
2. Submit the following documents:
a. Electrical drawings of Renewable Energy System.
b. A completed System Component Information Form.
c. Test and compliance certificate for inverters.
(These 3 would have to be prepared by the company installing your system.)
3. The Government Electrical Inspector (GEI) has to inspect the system and approve the drawings, and his certification should be forwarded to JPS.
4. Pay at JPS parish office for
a. Net Billing Meter (about Ja$50,000.00).
b. Utility Disconnection Switch (if that isn’t already in your system).
c. Deposit Upgrade - total of last 3 months light bills.
5. Submit proof of insurance, ownership of property and system.
A variety of solar panels is available with a range of prices.
Monocrystalline panels are more efficient than polycrystalline, because they continue to work at lower light intensities.
The wattage of on the panels indicates the maximum which they can supply in ideal conditions, i.e. at solar noon on a clear day at a temperature of 25 degrees C.
One would think that with all the sun we get in Jamaica, our systems would supply more current than those in a temperate climate. However, panels are dark in colour and are directly in the sun, so they get hot. Any increase in their temperature above 25 degrees C reduces their efficiency. Surrounding air above that temperature would not be able to cool them in the way a cooler temperature could.
Shading of the panels, including partial shading and cloud cover, reduces their performance. For example, in July, an array of 12 monocrystalline 300W panels produced a high of 21.3 KWH on a sunny day, and a low of 4.6 KWH on an overcast day, and an average of 16 KWH per day. As the system had battery back-up, not all of this was available for use.
Solar panels generate and batteries store DC (direct current), but household appliances use AC (alternating current). Inverters convert DC to AC. Today’s inverters are sophisticated, computerized pieces of equipment. There are different kinds for stand-alone systems, for grid tie, for grid tie with battery backup, and some can even incorporate generators.
Listed in the Jamaican Yellow Pages are about twenty companies which sell and install PV systems. Your choice of company would be influenced by their experience, expertise, and quality of relationships with customers. Having selected a company, you can partner with them in coming up with a design to suit your requirements. They would make a site visit to see where you propose to locate the panels and inverter, and batteries and charge controller, if you plan to have a battery back-up system; and recommend which brand of components you should buy.
With the cost of electricity as it is in Jamaica, most people have taken steps to conserve, replacing incandescent bulbs with fluorescent and now LED bulbs, and replacing electric with solar water heaters. The appliances which use the most electricity, and have the highest wattage, are those which heat and cool. If you have an electric stove, and have good reason for not wanting a gas stove, this will present a challenge.
A final word
Find out as much as you can about SV systems before you install, because whatever you buy becomes your responsibility.
The initial cost of the components is high, and they do require energy for their manufacture. It takes a solar panel about a year to recoup the energy used in its manufacture. All components of solar systems have to be imported into Jamaica, and require foreign exchange. However, in the long run, a large number of PV systems installed would reduce the country’s oil bill.
120,000 customers, each with 10 x 300 watt panels could provide 360 megawatts, the same amount of power as the new power plant to be built. Initial cost would be about US$ 1800 million, considerably more than the new power plant, and less reliable, but eventually could reduce the oil bill considerably.
Thanks to Solar Direk (in Montego Bay 979-7994 and Kingston 946-9860) for use of their photographs.