Photo Voltaic Collection Technology
(no solar concentration)

This technology is very much in fashion these days. So called, "flat panel" PV or "One Sun" PV is all the rage and a lot of money is being made installing these systems right now. The home owners installing these systems are taking a bit of a risk in terms of whether these systems will save them money, or decrease their carbon footprint for that matter. The risk is this:

Electrical energy is relatively cheap these days. PV panels are only about 16% efficient and they are expensive. PV panels also take a lot of energy to create by virtue of the fact that they need highly purified silicon. PV cells also degrade somewhat over time and are susceptible to damage by wind and hail. This means that folks installing PV now are taking advantage of government incentives and banking on two possible changes that will make their PV installation pay off. These two changes are:

1. The cost of energy will go up significantly. If the cost of energy (currently around $0.08 per Kwh right now) were to double or triple, a PV system would likely pay for itself a couple of times in its lifetime.

2. The latest technology being installed now will have a longer lifetime. If PV systems last at say 90% capacity for 10 or even 20 years, instead of the currently hypothesized 7 years, the a typical PV installation will again pay for itself a couple of times over.

If both these things happen in a big way. Then PV nay-sayers, like myself, will have to eat some serious crow. However, as things stand now, a standard PV installation is expensive and will likely need major maintenance or replacement about the time it has paid for itself (both in terms of dollars and carbon emissions). If you are financing a PV installation, you may never see a return on your investment.

The good news for people who have installed PV systems, is that both 1 and 2 are likely to happen to some degree. Certainly the cost of energy can only go up, and the current generation of PV cells is likely to hold up better than the previous generations by virtue of better heat dissipation and better films and glass coverings.

There are also some special circumstances which almost certainly makes sure a PV system will pay for itself. If there is any reason why a typical grid connected home is not practical or unreliable, then flat panel PV is an excellent choice. Flat panel PV has proven to be very reliable, has no moving parts, and a good installation will last for many, many years with now maintenance (other than dusting and maybe snow removal). If, for example, you are two or three power poles away from electrical power and you will need to pay to have those poles put in place, that cost alone tips the balance in favor of PV electric. If the area you are in has notoriously unreliable power company service, then just the reliability factor may make PV desirable.

This brings up another common issue with PV systems of all sorts. That is, what to do about both excess and insufficient solar capability. A popular option these days are grid tie systems. In this case, you are pumping power from the sun into the power companies grids and getting credit for any power you put in. Then you draw power from the grid just as everyone else does. So, you have all the power you may need for the power company and any excess power you generate goes to supplying the needs of others on the grid and you get credit for that.

In the case of grid tie systems, most power companies will offset your usage at the going retail power rate, but any excess power you provide above the amount of power you use in a billing period will be credited at the wholesale power rate. This means, from a financial point of view, it is in your best interests to have an installed capacity as close to your household electric needs as possible.

The other option for insufficient or excess solar capacity is to store previous excesses in batteries. This adds to the cost and complexity of the system, but is necessary for systems that are not connected to the grid in anyway. Some small amount of battery capacity might be desirable for those who chose PV because grid power was unreliable in their local. In that case, the battery capacity is meant to bridge the outages from the power company when they occur when the sun is not shinning. A small gas generator may be a more economical option in that case as batteries to bridge multiple day outages are very expensive. A combination of batteries to bridge an hour or two outage coupled with a generator to handle the longer outage is probably the best bet for this situation.