Energy efficiency at home

Posted by Renewcapa on 10/05/13
Tags: ,  

What exactly is an energy efficient home? Provided it meets with it’s owner’s energy demands, an energy efficient home is one that reduces energy waste by reducing unnecessary consumption of energy; consequently, energy efficient homes reduce their environmental impact by reducing emissions of greenhouse gasses. Comparing an energy efficient home with a conventional home, one can easily spot the differences in their respective energy behaviours; and energy behaviour translates to home energy bill, thus significant cost savings of energy efficient homes over conventional ones. (more…)

Increasing Solar panel efficiency

By solar panel efficiency we refer to the rate at which a photovoltaic panel converts solar energy into electrical energy. In general, a typical efficiency level of PV panels ranges between 12-16%, though recent technological improvements suggest we will soon be talking of efficiencies in the range well above 20%!

Solar panel efficiency

Solar panel efficiency is a measure of the solar cell’s ability to convert the solar energy to which it is exposed to into useful electrical power.  The solar panel’s energy conversion efficiency is expressed as a percentage of the cell’s output power (watts) over the input sunlight energy (irradiance in W/m2) and the surface area of the solar panel (in m2). Considering a solar panel with a surface area of 1 meter sq. (m2) and with solar panel efficiency of 20%, at standard test conditions, i.e. amongst other conditions at clear weather with irradiance of 1000 W/ m2 and temperature of 25 °C, it will produce an output of 200 watts.

Consequently, the solar panel used in our illustration above, will produce more power than the power output of (STC) on a clear day with the sun high in the sky and less power on a cloudy day or when the sun is low.

Given a constant rated power for two different solar panels, e.g. 250 watts, their efficiency level will determine their surface area respectively. For example, a solar panel with efficiency 10% will have twice the surface area of a panel with efficiency 20% given they have the same rated output wattage – see what size of solar panels for home

solar panel efficiency PV cell

Factors affecting solar panel efficiency

From above definitions, it can be easily understood that Solar panel efficiency is influenced by many factors. The most significant are gathered and presented below:

Types of solar panels

  • Monocrystalline silicone photovoltaic cells, or single crystalline solar panels have been considered to be more efficient primarily because they have been found to exhibit a higher peak efficiency; consequently, monocrystalline solar panels were historically used for residential installations where installation area is limited. However, the statement that monocrystalline panels are more efficient than polycrystalline solar panels is rather controversial and subject to manufacturers’ specifications.
  • Polycrystalline solar panels have, up to now, been considered less efficient when compared to monocrystalline sola panels. However, given latest technological evolvement, polycrystalline silicon has managed to cover this gap, if not to surpass the performance of monocrystallic, especially at temperatures higher than STC.
  • A third type of solar panel is thin-film solar panels which are less efficient than crystalline silicon cells but also cost less. Being less efficient implies that they need a lot more surface area than crystalline silicon based cells, but they are highly flexible, thin and can be installed onto many different surfaces especially on buildings (commercial or residential solar panels – see Solar panels for green buildings and Best research-Cell Efficiencies (NREL)


Depending on where you live, temperature may become a significant source of solar panel efficiency deterioration, especially if you live in a hot climate. The performance of solar panels may drop significantly at temperatures above (STC). One practical way of combating this is to use any means of ventilating installed solar panels to make them more efficient.

Tilt and orientation

To maximise effective exposure of the solar panel to sunlight requires that solar panels are faced to true South (for location sites within the North hemisphere) and vice versa. The inclination angle depends on the season and latitude of the site’s location; to increase exposure of solar panels to sunlight we can adjust our solar panels orientation 2 or 4 times a year according the season. Alternatively we can use a solar tracker, for maximised results, though trackers are mainly used to commercial application and not for residential applications, primarily due to higher costs and town planning restrictions.


Undoubtedly, shading will greatly affect the output performance of a solar panel. IT is important to note that when solar panels are connected in a module with one single inverter, the maximum module output is determined by the minimum performing cell; thus, in case of shade falling on a particular panel, it will influence the whole row circuit of solar panels connected together. That is why, especially in residential applications where shadings are more likely to occur, it is important to examine installation site, e.g. the roof of the building, and note any sources of shade in order to design the solar panel system accordingly. One possible solution to avoiding this solar panel bottleneck is with the use of micro-inverters; in any case, if you are planning to install solar panels for your home, it is advisable to ask for a proper installation design from potential solar panel installers in your area – you may want to see solar panels for home.


By exposing solar panels to sunlight, they are also exposed to all nature’s conditions, including rain and humidity. If humidity manages to penetrate into the solar panel frame, photovoltaic performance will be reduced significantly and might lead to permanent deterioration of the modules performance.

Lifetime and age

Manufacturers always quote expected efficiency levels of their solar panels across their life span. For example, a common quoted is manufacturer’s performance warranty of minimum efficiency within 10 first years to be above 90% of quoted solar panel efficiency and the respective figure between 10 and 20 years around 80% or 85%. A Typical degradation rate is 0.5% per year of use.

Cleaning and maintenance

Solar panels usually require minimum maintenance as they do not incorporate mechanical moving parts; however, because they operate on sunlight passes through glass to reach the solar cell, sunlight quality is of ultimate importance and thus cleaning of the solar panel, especially the panel glass, is very crucial. As solar panels are exposed to natural conditions they gather dirt, dust, bird droppings, etc. which lead to reduction of the effective sunlight reaching the solar cells thus reducing solar panel efficiency and generated output. In cleaning roof mounted residential panels it is always advisable to seek some professional solar panel cleaning advice as any misconduct in doing so may lead to scratching the photovoltaic glass and creating a permanent more serious problem. Usually, solar panels are cleaned with lukewarm light soaped water solution and a soft non-abrasive cloth.

Monitoring performance

Keeping an eye on solar panel performance and efficiency levels through real time on-line platforms is extremely important and highly beneficial. Having access to this continues real-time data will ensure high quality control and security over the photovoltaic investment and subsequently safeguarding energy production. Deterioration or sudden decreases in photovoltaic performance are spotted immediately, thus providing early warning to act proactively and effectively against threats. On line monitoring can provide useful data for deciding on solar panel cleaning frequency, solar panel orientation corrections, and on any sources of malfunction from an early stage.

The importance of solar panel efficiency

Simply put, solar panel efficiency influences how much electricity a solar panels system is generating; this means generating more or less electricity given a constant area of solar panels, i.e. space limitations on a roof, and constant solar panel wattage (solar panel capacity).  The factors influencing the output of your solar panel installation have been outlined and consist of exogenous, such as weather and location conditions, as well as endogenous sources to your solar panels, such as sola panel efficiency – you may want to refer to solar panels properties in solar energy pros and cons.  Irrespective of the solar irradiation potential at your area, obtaining the highest possible output, given your budget for solar panel investment, is a primal requirement. Solar panel efficiency directly influences your output yield in generated electricity (e.g. kwh/year) and consequently influences generated income from rebates or FITs for on-grid installations. Eventually, solar panel efficiency is a primal factor influencing financial viability of your solar panels investment and the end repayment of your solar panels cost. Apart from solar panel efficiency it is crucially important to note that we are always interested in the efficieny and output performance of a solar photovoltaic system as a whole. Efficiency of solar panels, on a single panel level, is only one variable in the solar system. Learn how efficiency of your solar panel system can be affected and how it can be optimised by shoosing the appropriate type of solar inverter in micro-inverter vs string inverter.


cell efficiency records (NREL)

Green Roofs can Boost Photovoltaic Panels

Posted by Renewcapa on 14/03/13

green roof gardenWhat is a “green-roof?” Some say the term conjures up images of green vegetation on a building’s roof; others refer to the concept of making a building’s roof green from an environmental standpoint with green energy solar panels. It turns out that green vegetation on your roof can actually help boost your roof-mounted photovoltaic panels.

Green building roofs

Keeping a garden on the roof is an eco-friendly solution that helps increase the energy performance of a building as it reduces unwanted heat gains in the summer and heat losses in winter – (see green buildings: Rational solutions). The soil and insulation and waterproofing materials that form the infrastructure for planting a roof garden act as an effective insulation for the building at the place where most energy losses occur – the roof. In summer, radiation heat is reduced as it does not reach the roof, thus does not enter inside the building, whereas, in winter, it acts as an effective insulation that keeps the required internal heat inside. The end result may result in energy savings for the building of up to 30 percent.

In addition, apart from the immediate cooling effect of a roof-garden building, green roofs in a community may lead to a micro-climate cooling effect that may be beneficial to the broader related area and community. Consequently, green roofing may help combat “heat island” effects in urban areas – a term used to describe the accumulation of heat buildup in urban areas that eventually remain hotter than rural surroundings.

Research documented in Green Roof Valuation shows that vegetated rooftops can facilitate solutions of complex environmental problems in urban areas. The report suggests that green (vegetated) rooftops, when compared to conventional rooftops, may yield a Net Present Value (over a period of energy savings for up to 40 years) that is 20–30 percent lower; thus, a viable investment over conventional rooftops.

Specifically, the initial additional investment required to make a roof plantable with green vegetation can in fact be recovered, through energy savings, by the time an alternative conventional roof would need replacing. In addition, findings suggests that green roofs may help improve the quality of the urban air, yielding additional benefits in monetary terms and reducing harmful atmospheric emissions. An illustrative example is that a 2000 square meter green (vegetated) roof is estimated to yield approximately $900 to $3300. Consequently, maintaining well vegetated roof-gardens may lead to significant financial, environmental and aesthetic benefits primarily from saving conventional energy but also through urban air quality improvement, and micro-climate cooling effects.

How green roofs can help boost photovoltaic panels’ performance

solar panels on green roofIn addition to these benefits of maintaining a green roof garden, a green roof can boost the performance of roof-mounted photovoltaic panels. One of the biggest and most significant performance parameters of photovoltaic panels is temperature, thus solar panel manufacturers specify their temperature coefficient. The performance boost by combining a solar roof-garden with solar photovoltaic panels has been the object of various research teams; findings suggest a boost effect around 15-16 percent output more than conventional roof mounted panels (i.e. without green vegetation). The increase in photovoltaic performance is mainly due to the cooling effect of the green garden, which is magnified in hot climates and during the hot summer season. An illustration of this result can also be found by comparing the output performance of a photovoltaic panel when it is installed in urban areas (e.g. on a conventional rooftop) with the corresponding performance when installed in rural areas.

Consequently, when having to make a decision about either of these solutions, it is important to note how the combination of both roof solar panels and a green (vegetated) roof, can offer extended benefits that are financial, environmental and architectural. Combining the energy savings from a roof garden, together with the boost effect on the performance of photovoltaic panels, can help reduce the cost of solar panels (see – how much solar panels cost) , thus making photovoltaic panels financially more viable especially for residential applications (solar panels for home).

source: green-roofs-boost-photovoltaic-panels

A guide to home solar panels

Posted by Renewcapa on 27/01/13
Tags: ,  

Whether you are interested in installing solar panels for your home or looking into a commercial solar photovoltaic power plant, before commencing on such an investment you need to identify what your project entails and assess its financial viability. Herein we provide some essential advice on making such an assessment of solar panels for your home. (more…)

How much do Solar Panels cost? – 2012 updated prices

Posted by Renewcapa on 21/11/12
Tags: ,  

Photovoltaic Solar panels cost has been diminishing drastically in the past years and is expected to continue its down slope for some time; the cost of solar panels is a variable that actually depends on the time, place and scale of your solar panel installation. (more…)

Net Zero energy homes and Zero energy buildings

The definition of zero-energy-home or zero energy building is often misunderstood as a building having zero energy consumption. A zero energy building simply refers to a building producing the same (or more) amount of energy than what it consumes within a single year. (more…)

Solar energy facts – US-2011 Solar Energy findings – Solar Energy prospects for 2012

US Solar photovoltaic (PV) market is healthy and booming, with Solar energy installations expected to grow further in 2012. According to the US Solar Market Insight report for 2011 and the GMT Research, US solar Photovoltaic (PV) installations have more than doubled, (more…)

Renewable energy facts: Energy storage is key for RES penetration into power generation.

Energy Storage is key for Renewable Energy Sources’ penetration into power generation. Renewable Energy Sources (RES) have become of particular importance in the establishment of green, environmentally friendly applications; thus they constitute a crucial piece of the puzzle for achieving global environmental, economical and social/political sustainability. (more…)

Solar energy facts – solar energy alone can power the world!

When we talk about renewable energy sources (RES), we define them as replenishable energy sources freely available by nature, such as solar energy – solar energy facts, wind energy, biomass/biofuel energy, water energy and geothermal energy. To exploit renewable energy sources (more…)

Green buildings: bioclimatic design, passive energy systems and renewable technologies

When we talk about green buildings we refer to the application of techniques and principles for reducing the environmental footprint of ‘having’ and using a building – see intuitive environmental awareness. Constructing and maintaining a green building incorporates applying green principles at all stages; designing, building and using it.

In general green building practices may be divided in to two main categories; passive energy systems and active energy systems aiming at energy efficiency, energy saving and exploitation of renewable energy. (more…)