Friday, November 20, 2009

hardware is here!

We have just received 10 200-W solar panels and the 4 kW inverter. I will post photos soon. We are aiming for installation the first week of December.

Thursday, November 12, 2009

tax credits for Puerto Rico solar power installations

Prior to the passage of law 248, the Puerto Rico legislature created the Administración de Asuntos Energéticos (AAE) to monitor and regulate solar electricity installations in Puerto Rico.

I read law 248 of 2008 (in Spanish) last night. There are a few useful points to highlight.
1. The 75% credit was during Puerto Rico fiscal years 2007-2008 and 2008-2009.
2. The 50% credit applies for FYs 2009-2010 and 2010-2011.
3. After FY2010-2011, the tax credit is 25%, and this seems to extend for an indefinite period.
4. The credit applies to both the equipment and installation, although it also applies only to equipment that carries 5 years or more warranty.
5. The equipment must be installed and certified by solar-licensed electricians and engineers.
6. The tax credit can be carried over for up to 10 years, so if for some reason you cannot receive some or all of the credit in one year, you can carry it over to the next, for up to 10 maximum. This may be important, as the total available in tax credits for any given FY is limited.
7. The tax credit can be transferred once.
8. Apparently, the documents that are required for the tax credits must be submitted with one's tax returns for 6 years following the installation.
9. The sales tax (the famous IVU) does not apply to the acquisition of solar electric equipment.

Later, I will detail the process of applying for the tax credit.

finalizing specifications

Choosing a grid-tied system has its costs. The main one is that when the utility power goes down, so does the solar electricity. This is for several reasons. First, "grid tied" means what it says, tied to the grid, not to the house. It serves to mitigate some or all of the use of grid power, but the house still runs off the grid. Second, the house cannot run off power from the panels alone (inverted, of course). This is because of the fact of brownouts caused by clouds passing in front of the sun, or surges in demand. So a storage system is required as a buffer. This consists of a battery bank, which I decided against for reasons detailed below.

Our contractor visited with the solar energy engineer on Tuesday. They measured the estimated average daily production based on the hours of sun that can be expected per day. This measurement consists of first, a device that records the sky exposure of the site. Based on the annually integrated solar track, shadowing from trees, adjacent buildings, even our TV aerial, cloud-cover data for our location, and other parameters, it computes a number that they claim is quite reliable. In our case, we will get an average of 5.4 h/day of production. This comes to 300 kW-h/month, which is just over half of our energy usage.

We will purchase 2 kW in panels, but with a 4 kW inverter, so if we choose to add capacity, it means only additional panels. The panels are 200 W models from Canadian Solar. The inverter is a Sunny Boy 4000US. The reason to forego the batteries that would have given us a standalone system is mostly cost. The batteries are expensive and short-lived. In fact, I calculated that whatever we save in electricity costs, we will spend in replacing battery cells, which have roughly 5-year lifetimes.

Our contractor is PR Green Tech Corp. Julio Correa, the owner, is friendly and attentive, and appears to be quite devoted to his avocation. I hope this will serve us into the future as technologies evolve.