Your home will still be connected to the National grid. If your solar panels are producing less electricity than your home is using, or at night time, you will receive electricity in the normal way.
No. In Solar PV panels the glass protecting the solar cells has an anti-reflective coating which greatly increases the transmittance through the glass to maximise the light reaching the solar cells. The outer face of the glass has a slight granular texture also intended to maximise yield. These two characteristics greatly reduce reflection from the glazed front face of solar PV modules.
Solar PV systems have no moving parts and require no maintenance. Most of the time the rain will keep the modules clean. However, a build up of dirt can affect system performance. The degree of soiling will depend on the location but usually dust accumulation and self-cleaning reach a steady state after a few weeks if the array tilt is at least 15 degrees.
A basic PV module (interconnected, enclosed panel of PV cells) has no moving parts and can last more than 30 years. There are examples of 35 year old systems operating at 95% of initial specification. Most manufacturers guarantee panels to operate at 90% of specification after 10 years and 80% after 20 years, i.e. 1% degradation a year. The best way to ensure and extend the life and effectiveness of your PV system is by having it designed well installed & maintained properly.
Most problems occur because of poor design or sloppy system installation, e.g. failed connections, insufficient cable size, components not rated for DC application. The next most common problems are failure of the electronics in other components of the systems e.g. inverters, which typically come with a 5 year warranty.