solar efficiency

We can talk of energy efficiency in technical terms - involving in this case the efficiency of a solar cell or panel and the light-to-power conversion efficiency or other related issues.

But we can also talk of solar efficiency in more immediate terms, stressing the limitations (and insufficient efficiency) of some solar applications, or the situations where they are too expensive, and also the situations where the existing solar efficiency provides cost-competitive solutions.

And it is this last sense of solar efficiency - in home applications - we are going to use here, in this page.

Solar Efficiency and Sun Resources

Solar resources and solar efficiency vary: solar map from Kyocera As expected, solar efficiency depends on the site's solar resource, more exactly, on the number of hours of sunlight. And also on the impact of the surrounding landscape (including the shade of buildings and trees...), the orientation of the solar panels to the sun, the tilt of solar panels, the design of the system, proper installation or the the type of solar panels...

See: Solar resources and solar performance

Solar efficiency in water heating

Solar water heating is a competitive solution. Efficiency in this area hasn't improved significantly over the last decades, but solar water heating systems are sufficiently efficient to compete not only with electric water heating but also with gas and other fossil-fueled solutions.

Just be aware to the differences between solar designs and panels. Solar efficiency depends on the type of solar panels (tube solar panels, flat solar panels) and design (thermosyphon, drainback...) which also depends on climate. Tube solar panels and thermosyphon designs (in moderate climate) or drainback systems (in cold climates) are very efficient and recommended solutions...

Be also aware to the fact that good energy-efficiency doesn't mean that typical solar systems do not require a backup gas system for peak demand periods and for very cloudy days.

See on these issues: Solar Backup

Solar efficiency in air heating

We can use solar heated air to warm our rooms (solar air-space heating), or we can use hydronic systems (water heated by solar panels in baseboards or radiant floor heating)...

But be aware with the solar energy-efficiency of these solutions. The efficiency is low or relatively low, and the designs and the role of the various solutions related with them are often partial and limited. These solar solutions aren't good enough in many climates and should only be used to supplement other heating systems and solutions. Besides, they can pose compatibility problems and may demand high initial investments.

See on these issues: Solar space heating

Solar efficiency in pool heating

Solar pool heating is a common, tested and competitive technology. The solar efficiency is, in this case, good. See: Solar Pool Heating

Solar efficiency in home cooling

Solar home cooling (solar air conditioning) is an emergent and promising technology with some decades and some recent novelties - namely the absorption chiller systems. Sun resources can make the solar efficiency of this technology too low, namely in home applications.

See: Solar Air Cooling

Solar efficiency in power generation

Solar PV (photovoltaic) systems for power generation is at a turning point. Their uses are increasing, and prices are coming down (due mainly to the huge investment of the Chinese in new factories and to the investment and know-how of big multinational corporations).

But without state rebates and tax incentives solar electricity is not energy-efficient enough. That is, photovoltaic efficiency is still to low to compete with the electricity coming from nuclear reactors or coal plants.

Monocrystalline and polycrystalline PV panels haven't improve enough in the last decades to become an alternative to the electricity from fossil fuel or nuclear sources. But recent progresses in another type of solar PV technology - the thin film technology - can change the rules. Solar efficiency in this domain is expected to rise sharply in the next few years.