Tuesday, November 25, 2014

PV electricity generation is not that complicated

The process of generating electricity with a photovoltaic solar system is not as complicated as many people think it is. It's actually a rather simple process that consists of several different principles. The basic principle is at follows; once the sunlight hits the surface of the PV panels the electrons in the solar cells get activated. The activation of electrons means that they start to move with much bigger frequency, and in the process they start to bump into each other more frequently. This interaction between the electrons is what generates electricity.

A solar (photovoltaic) panel or module consists of large amount of individual solar cells. If we were to simplify things we could say that solar cell is primarily silicon with some circuitry. The more cells there are in a solar panel, the more electricity it can generate. A string of panels makes up an array and multiple arrays comprise a solar PV system.

If we were to divide things even further we could say that PV system is only one form of harnessing solar energy. For instance, hot-water system is used specifically to heat water while A Concentrated Solar Power system (CSP) uses mirrors to focus sunlight on water, causing it to boil producing steam, which is then used to generate electricity.

PV systems are in most cases connected to the grid with the only real exception here being people in more remote locations where a battery back-up system is often lot more practical. Two primary types of solar panels are mono-crystalline and polycrystalline.

Silicon is the primary material used in solar panels as the main active material in a solar cell, primarily because of its unique chemical properties. A silicon atom is comprised of twelve electrons on three separate 'shells' or layers. The outermost 'shell' has four electrons that are highly reactive. The outer electron shell of a silicon atom is seeking to reach of state of equilibrium by 'sharing' its electrons with other atoms. Conversely, those other atoms will share their electrons as well.

These electrons are always moving but the energy from the sun causes their rate of movement and interaction to increase. By bumping into each other more frequently they generate friction and this is what generates electrical energy. After this phase it is only a matter of channeling the current through all the wiring to the inverter. The inverter is needed to convert the electricity from direct current to alternating current because our electrical grid is not designed to handle direct current. In a grid tied system any excess current is supplied back to the grid. In off-grid PV system there is usually a battery back-up system to store excess current generated by the system for later use.

Generating electricity from the sun is a very practical way to meet our electrical demand, especially because solar panel prices have decreased by more than 70% in the last five years. This particularly applies to remote and isolated areas where using PV panels to generate electricity is far more efficient than rebuilding entire energy grid.

Friday, June 20, 2014

Latest research on environmental impact of wind turbines

Offshore wind farms and noise pollution issue

Although majority wind turbines are built on land there are also many suitable offshore locations where offshore wind turbines can be built. Offshore wind energy projects have lately become very popular in some countries of the world, most notably United Kingdom and offshore wind energy is set to play major role in global clean energy market in years to come. Offshore wind energy projects can provide better efficiency compared to the wind energy projects on land because of powerful winds that are also more stable and frequent as compared to those that blow on land. The major drawback is however construction costs, being significantly higher for offshore wind energy projects since they need to be constructed to withstand extreme weather conditions.

Growth in offshore wind generation is expected to play a major role in fight against climate change issue by meeting carbon reduction targets around the world, however the environmental impact that offshore wind turbines have on marine life hasn't been much researched as is also the case with the impact of construction noise on marine species. There could available be a lot more information about this matter because the scientists from the United Kingdom and the United States have recently managed to develop a method to assess the potential impacts of offshore wind farm construction on marine mammal populations, with the special emphasis on the noise made while driving piles into the seabed which occurs while installing wind turbine foundations.


The researchers report that pile driving during the construction of offshore wind farms produces a staggering amount of noise which is potentially harmful to marine species. This is particularly hazardous for already endangered marine species, such as protected populations of seals, dolphins and whales.

The researchers studied ongoing construction in and around the North Sea, where many proposed wind farm sites are on submerged offshore sandbanks. These sandbanks provide important habitats for many different marine mammals and seabirds. Several previous researches focused their attention on the potential impacts to birds, while this latest comprehensive research tries to assess the potential long-term impact of construction on protected marine mammal populations, particularly harbor seals. In United States where offshore wind power development is set to grow rapidly in years to come, this type of assessment could be applied to wind turbine construction that may impact a number of endangered species, including three whale species: the North Atlantic right whale, the humpback whale, and fin whale.

This study aims to present takes a worst case assessment of the short term impacts of noise pollution coming from installation of offshore wind turbines and how these negative effects of excessive noise may influence longer term population change. The information gathered from this study should provide information that would allow regulators to balance their efforts to meet both climate change targets and existing environmental legislation thus paving the way for sustainable offshore wind energy development.

It has been reported that harbor seals can be impacted by the noise pollution in several different ways. Particularly damaging loud construction activities can cause traumatic hearing injury or even death at the close range while little bit less loud noise pollution levels could lead seals to avoid the area and lose favorite feeding grounds, potentially causing greater competition in other areas thus leading to problems with finding food which could negatively result in lower reproduction or survival rates. Also, the changes in hearing sensitivity could make seals more vulnerable to predation, thus further reducing their numbers and putting their future survival in question.

Bat deaths from wind turbines – Exaggeration or not?

Several different studies were studying the impact that wind turbines have on bat population. There hasn't been a general opinion on this matter with some studies reporting minimal bat dearth rates while other reporting alarming bat death rates.

A brand new estimate of bat deaths caused by wind turbines concludes that more than 600,000 of bats have probably died in 2012 in the United States. This latest estimate is published in an article in Bioscience and has caused plenty of controversies. The researchers   used sophisticated statistical techniques to predict the probable number of bat deaths at wind energy facilities from the number of dead bats found at 21 locations, correcting the statistics for the installed power capacity of the facilities.

Many people care very little about bats, but nonetheless they play an important role in the ecosystem because of their role as insect-eaters, not to mention that they also pollinate some plants.

How are bats killed by wind turbines? It is not only by collisions with moving turbine blades, but in some cases also by the trauma resulting from sudden changes in air pressure that occur near a fast-moving blade, particularly in large wind turbines.

Mark Hayes of the University of Colorado says that 600,000, although a big number is still a conservative estimate with the possible actual figure 50 percent higher. The data that Hayes analyzed also leads to conclusion that some areas of the United States might experience much higher bat fatality rates at wind energy facilities than others and it has been reported that the Appalachian Mountains have the highest estimated fatality rates in entire United States.

The consequences of deaths at wind farms for bat populations are hard to assess ad give exact numbers primarily because there are no high quality estimates of the population sizes of most North American bat species. Wind farms are just another negative factor in the line for bat populations because these mammals are already under stress because of climate change and disease, in particular white-nose syndrome.

Conclusion

One can not say that using wind energy is perfect from environmental point of view because every source of energy, renewable or not, has some negative environmental effects. In any case, using wind energy is definitely better for environment than staying with fossil fuels. Of course, future technological development must go hand in hand with the protection of species such as whales and bats, and thus we need to make future wind farms, offshore and onshore, as environmentally friendly as possible because this is the only way to ensure sustainable wind energy development.

The overall effect of wind turbines still remains more positive than negative, particularly in comparison to environmental damage done by currently dominant fossil fuels (climate change, different forms of pollution). There is still plenty of room to improvement and wind project developers need to apply different technological innovations in order to minimize the damage done by installation and operation of large wind turbines. Hopefully, future research will provide new environmentally friendly technological solutions for wind turbines. Some positive examples already exist such as for instance equipping turbines with radars to protect birds from colliding with its blades.