Introduction
A local grocer in Parras decided that he would like to go solar. But he wanted to know if it would even be possible, let alone affordable, here in Mexico before making any commitments.
Method
Our first task was to discover the energy demand of his business. It was difficult to determine at first, since his house and the store were both connected. But he gave Mel and I a copy of his highest bill of the year, and we went from there. We decided to go through the store and do an energy audit just to make sure that the bill was really the highest demand. it wasn't too difficult considering that he didn't run much in his store. We came to some pretty close numbers, and decided to run with it.
| Load | Run Watts | Hours/day | Days/week | Total wattage |
| Criotec Refrigerator | 460 | 6 | 7 | ? |
| LaLa Refrigerator | 498 | 6 | 7 | ? |
| Freezer | 460 | 8 | 7 | ? |
| Television | 60 | 8 | 7 | ? |
| T8 Lights X 4 | 128 | 6 | 7 | ? |
| CFL Light | 24 | 6 | 7 | ? |
| Total: ? |
Our next task was to hit up the Comision Federal de Elictricidad, to see if grid-intertie is possible. We got quite the run-around here, and eded up talking to the mayor as well. We could always use the battery approach, but it costs so much more that way. We found that there was some legslation passed that makes the grid-intertie possible, but had trouble sifting through the many pages of Mexican law. We finally got through to the main man at the C.F.E., who told us that grid-intertie is possible, if we submit a plan and make sure to have an automatic shut off, just in case the power goes out and needs to be worked on; he was concerned about the safety of the workers in the area. Once that was established, we decided to make two reports, one for the battery system, and one for the grid-intertie, just in case. We then had to search for the peak sun hours of Parras. There's some information about Saltillo and Monterrey, but since Parras is such a small town, it was difficult to track down the information we needed. It wasn't until we were able use RET Screen and the NASA website that we had breakthrough.
Materials
We decided to source the materials from the system from Mexico, if possible. That was difficult, until we were able to contact to one of the main suppliers through email. based on the energy need of the store, we wanted to use some kind of 12V battery. Using the RET Screen System made things a lot easier for us. We were able to input the battery size and price, and even calculate the effect of the tilt of the sun during the year.