Lloyd’s roof-mounted solar panels (image via Extreme Tech)
1. Roof Mounted Panels Suck – They often have limited or no tilt control and clumsy to maintain. This means that you will likely get strong performance in summer or winter, but not both. Finding the average latitude tilt for your region and mounting the panels at that angle is your best option for roof mount. Trackers can bring your performance up by 1/3rd, but will include extra expense and complexity. Consider a manual tracking system which you just push with your hands through out the day if you need a early morning or late afternoon boost. This is ideal for the off-grid / unemployed eco-geek.
2. Grid Tie has issues too – Although grid-tie allows a PV install to greatly reduce their installation time and costs they also have some drawbacks. Continuing to buy power from a power company can result in relatively high monthly fees if the system purchased was undersized. Many grid-tie installations have no battery backup so when the grid dies, you lose all your juice too. In remote towns many power companies only pay the customer a 1/4 of what they charge the customer for power. My town being unusually behind the times refuses to purchase any power from their customers.
3. PV Batteries – New batteries are easy, but old ones can be fixed. Our world is hemoraging so called “dead cycle batteries”. Try talking to your local golf course, marina, or auto parts store. As you learn to test cells and repair lead acid batteries through desulfation you can save yourself a fortune in batteries and store large amounts of energy. Keep in mind that batteries are much like people. They like 72F temperatures and a little exercise. Do not cycle the batteries below 50% on a regular basis. I try to stay over 70% capacity on my battery array at all times.
4. Heat – My panels tend to have a pretty big drop off in performance during the summer. This is partly due to my not adjusting the PV array to be almost flat during June. It is also related to our monsoon season bringing in lots of rain and cloudy weather. However, the real killer of performance is the temperature. High temperatures drop my panel performance by 30%. Our temps in June sit peak around 100F in June which is enough to dramatically reduce the performance on a polycrystal PV cells. The monocrystal cells are supposed to handle the higher temperatures better.
Thanks Mikey (and Lloyd!)