Solar Power Eco-Development Engineering Questions?
I’m considering integrating solar power systems and components into an eco-development here in Costa Rica. I have some questions in order to budget for these systems:
I cant determine if we need a “grid-tie” system or an “off-grid” system. I believe we need parts from both, or a “hybrid” system. I want to offer solar power as a standalone system with a large battery backup that utilizes the solar power until the batteries are exhausted. When there is no power left from the batteries, it would automatically switch to local power company, only as a backup. It is doubtful that the local government-controlled power company would issue credits for “selling power back to the grid”, so a “grid-tie” system as shown on your packages would not work. The energy from the solar panels would have to route into a large battery bank, not back to the grid. It is also different from an “off-grid system” in that, if depleted, the system would need to automatically switch to local power source.
This solar power system would need “pure sine wave” inverters - capable of supplying energy to any standard appliance as well as a sensitive automation control system with touchscreens in the home. I believe the Magnum MS4448 (http://www.wholesalesolar.com/products.folder/inverter-folder/Magnum_MS4448.html) fits the bill, but I’m not sure.
Finally, I would like to link 7 of these eco-home solar power systems together in order to capitalize on power sharing for a more reliable and robust system - especially since it is likely that at least 1-2 homes would not be occupied (they’re vacation properties) at any given time. I believe that by burying Romex electrical lines between the homes and linking each homes’ bank of batteries would do this… correct? Then, just one of these systems would be linked to the power company to switch over once all batteries are drained - since the charge would be evenly dispersed across all homes…. correct?
I would use locally-bought marine-grade batteries for storing charges in each eco-dome. I’m not sure how many batteries or what type. I would want each 2,000 sq.ft. eco-home to be as self-sustaining as possible on solar power. Assuming a maximum power draw of 500KWhs per home per month, what parts do I need? (I’m looking at the website: www.wholsesalesolar.com for parts to import)
Also, is there a better way of doing this, or do any of these ideas seem unfeasable?
Thanks
February 24th, 2009 at 7:16 pm
Your system is basically doable.
As to pure sine wave inverters, these do not truly exist. All inverters work by taking the DC voltage from the batteries or other source, and chopping it onto the output lines. This is done with solid state devices such as IGBTs. The smoothness of the output power is determined by how fast the DC level is switched. All inverters put out high frequency harmonics. The general method is to run the output of the inverter through an inductive device such as a transformer, the reactance of which tends to smooth out the switching impulses.
Many home appliances could care less about the noise on the power lines. Some home electronics are sensitive and should be run of inductively isolated circuits. Your phone system is most likely not all that susceptible, it probably has it’s own power supply that creates the local voltages. These supplies are usually switchers these days, which are just a variation on an inverter. I would talk with the phone system supplier to determine if there is a problem.
Batteries: I would place all the batteries in a central location, for safety and connivance. As to the number of batteries needed, you will need at least 15 in each bank to give you 160 VDC. This will then come down to the 120 VAC that you will want out of the inverters. The total number of batteries you will need is dependent on the peak instantaneous current demands of your systems. The current draw can be determined by I = E/P where I is the current, E is the voltage, and P is the power. You list 1/2 MegaWatt per home per month, but what usage do you expect at any given moment. The 1/2 Mega Watt per month would only come into play if you intended to run the entire system off batteries for one month, and I’m sure that you don’t want to do that. You need to determine how much power you will be supplying at a given time and size your battery array to that usage.
February 25th, 2009 at 9:46 am
You are going to need a lot of solar panels.Where do you plan to get the solar panels?those are the most expensive stuff for solar power system.