Yes, it is possible. Photovoltaic solar energy can be combined with other types of electricity generation, either renewable or conventional sources. For example, you can install a PV system with support of mini-Eolic, mini-hydro energy, etc. These Installations are called hybrid installations.
In fact yes, but it is more recommended, use both solar batteries, specially developed to discharge slow and deep, and solar cable (prepared to withstand high operating temperatures).
Usually the production guarantee for the panel is 90% for the first 10 years and 80% until 25 years. Now there is a linear guarantee of production, in some cases it decreases 0.7% / year from 2 to 25 years, so follows a certain relation with the aging of the panel and, therefore, a more real guarantee. What is the Photovoltaic power plant production capacity? Depends on where you install it, inclination and solar orientation, for example a 20kW installation in Valencia with south orientation and inclination of 35º can produce 31700kWh / year.
Self-consumption, off-grid installation, generates electricity for the producer-consumer in remote locations without access to the power grid. The self-consumption installation connected to the network can be by net metering (already in place in several countries): when the excess of produced energy is injected in the network and is returned when it is needed or is a system connected to internal network with the objective of reducing the consumption of electric energy from the grid. Currently, the latter can be useful for trades and industries that consume electricity during the day (fruit warehouses, frozen industries and farms).
The guarantee of photovoltaic panels is a controversial subject, sometimes difficult to treat. Let's take the example of buying a 100W panel and one week later detect a loss of power. If the panel characteristics indicated a tolerance of +/- 3% that means that our panel could be generating 97 W in STC. If the warranty covers 90% of the actual power, to claim for production guarantee, the panel should be producing less than 87.3W, without taking into account the error margin of the measuring instruments that can be 1% to 5% depending on the machine used. In these cases it is good to have an experienced authorized distributor who first analyzes the quality of the modules supplied, and second, if applicable, to be able to negotiate the warranty conditions direct with the manufacturers to defend the rights of customers in case of Claim of warranties.
The data to be used at the time of sizing a solar system PV for self-consumption are location, orientation, slope of the surface on an installation platform and calculation of shadows and wind. It should also be analyzed the consumption profile, considering the following details: consumption curve, measured peaks, distribution of the same throughout the day and possibility to shift certain consumptions during the day. Once all these data are extracted, we study the combination of the most appropriate photovoltaic components for the installation.