About Solar Energy : Challenges of Solar Energy

Some of the Challenges in Solar Energy Production

• The efficiency of solar panel

• High initial capital and maintenance cost PV Energy system

• Land scarcity and decreasing property value

• Lack of skilled workers

• Intermittency and Power Quality issue

• Scarcity of material for PV cells

• Environmental downside

Solar Panels Efficiency

The average Solar Power upon the Earth's surface is 174.7 watts per square meter and in one hour, the sun provides about 3.21 x 10^20 joules of energy to Earth.

That's equivalent to 76,841 megatons.

In less than two hours, the sun provides more energy than the entire planet used in a year.

But only a small fraction of this energy can be converted into solar energy due to the less efficiency of solar cells.

A solar panel is a combination of solar cells which are connected in series or parallel to make a complete solar panel.

Concentric Solar cells contain light energy absorbing material and convert it into electrical energy.

The solar cell efficiency is limited because only one electron can be excited by one photon, regardless of the photon energy or energy packets that are available in sunlight.

The solar PV cells also have limited maximum efficiency, known as Shockley-Queasier limit.

The maximum solar conversion efficiency of a solar cell with a single p-n junction is approximately 46% (theoretically) with concentric sunlight and in-lab data it has reached 27%.

For commercial use, this efficiency is just 16% of the total size of the cell.

It means that when sunlight falls on solar cells it only convert 16% of sunlight energy for further use and the rest of the energy is going wasted.

High cell efficiency provides a lower unit cost, because it requires less surface area to generate the same watt peak of electricity (Wp - the output power generated by a solar cell under full solar radiation), thus decreasing the required number of cells.

In short, with efficiency improvements, Solar Power generation technology could have significant potential as an energy resource.

High Initial Capital and maintenance cost of PV Energy System

Although the installation of solar panels would bring immense benefits in the long run, the upfront costs can be punitive.

Solar panels also require inverts and storage batteries to convert direct electricity to alternating electricity to generate electricity.

While installing a solar panel is quite cheap, installing other equipment becomes expensive.

Depending on the company you choose to buy solar panels from, it could cost an arm and leg.

It's even difficult to quantify the entire cost of installation without the help of manufacturing companies.

Some nations have introduced rebates and tax credits to enable lots of people to install solar panels, but unless you are putting some money aside for this, it can be an unbearable cost.

Also, it might take up to 10 years to 15 years before you can break even with your initial investment.

It's not about how much the payback period is.

Anything that can reduce our dependence on fossil fuels is worth trying.

Installation and maintenance, in particular, are often underemphasized, but it is just as important as the other challenges that make solar-powered electrification a tricky prospect.

Another challenge has to do with how transactions to purchase solar panels are structured.

Most solar panel installations are a one-time transaction where a customer pays for the panels, equipment, and installation.

The company delivers these products, then either installs the panels themselves or hires independent installers.

In these deals, it is often unclear who will pay for maintenance when the solar panels break down.

Many companies have little financial capacity to bring repair technicians out to remote locations years later to service panels (aside from reputation and customer satisfaction, which some corporations are not necessarily interested in) since most are struggling to make money as it is.

Customers are often not in a position to pay much extra for maintenance either since they already paid a large up-front premium for the installation.

Hospitals, schools, and businesses cannot afford to continue pouring money into solar systems that unexpectedly break down after two years when they were supposed to work for twenty years.

But if no one is able or willing to pay for maintenance, the panels go unused and wasted.

Land Scarcity and decreasing property value

Another concern is that solar energy may take up a significant amount of land and cause land degradation or habitat loss for wildlife.

While solar PV systems can be fixed to already existing structures, larger utility-scale PV systems may require up to 3.5 to 10 acres per megawatt and CSP facilities require anywhere from 4 to 16.5 acres per megawatt.

Depending on their location, larger utility-scale solar facilities can raise concerns about land degradation and habitat loss.

Total land area requirements vary depending on the technology, the topography of the site, and the intensity of the solar resource.

Unlike wind facilities, there is less opportunity for solar projects to share the land with agricultural uses.

However, land impacts from utility-scale solar systems can be minimized by sitting them at lower-quality locations such as fields, abandoned mining land, or existing transportation and transmission corridors.

Smaller-scale solar PV arrays, which can be built on homes or commercial buildings, also have minimal land use impact.

In recent years, publicity surrounding solar farms has gained the attention of property owners and appraisers.

As with any large-scale development, the change represented by utility-scale solar can be cause for concern.

Naysayers express worries involving impacts to shed, drainage problems, the idea of replacing productive agricultural lands with industrial use, and more.

Much of this worry comes back to one thing: the potential impact on property values.

A recently completed study at 400,000 transactions in New England over 15 years, finding that suburban residential property values suffered negative impacts when nearby solar farms replaced resources perceived as scarce, such as green space.

On the other hand, this same study found no associated impact on property values for solar farms located in rural areas.

However, the impact can be reduced by placing facilities in low-quality areas or along existing transportation and transmission corridors.

Lack of Skilled Solar Energy Workers

One major hurdle for installing solar panels is the lack of skilled workers to do the job.

Customers for solar panel installations could range from hospitals requiring over 20 kilowatts of power to small villages needing less than 500 watts to power the entire village.

Some training is necessary to understand the complexities of these systems.

This problem is being approached in a few different ways.

Some companies are hiring and training dedicated installation crews to travel around vast areas doing the work.

The problem with this arrangement, though, is that traveling between job sites is inefficient, and any downtime becomes very costly for companies trying to keep dedicated crews on the payroll.

On the other hand, if these companies hire independent installation crews then ensuring quality standards is harder to do.

Also, companies are at the whim of the rates that the independent crews set.

Not to mention, in some areas there are no independent installation crews for hire.

Availability of appropriately skilled manpower is one prominent challenge and the solar sector may benefit from employing workers from conventional labor markets with relevant skill sets.

However, the United Nations Development Program (UNDP) is stepping in to help.

Recently, in Mali, the UNDP paid for the training of female solar technicians to perform installation, maintenance, and service for their entire village.

Not only does this solve one of the difficult problems with solar installations, but the training also provides an economic boost for the entire village.

Women are now able to earn a living wage to help further support their families.

Intermittency- Power Quality issue

One of the biggest problems that solar energy technology poses is that energy is only generated while the sun is shining.

That means nighttime and overcast days can interrupt the supply.

The shortage created by this interruption would not be a problem if there were low-cost ways of storing energy as extremely sunny periods can generate excess capacity.

As the global capacity for Solar Power continues to rise, nations like Japan and other global leaders in solar energy technology are focusing on developing adequate energy storage to deal with this issue.

While integrating PV system with grid, the most significant parameter is power quality.

Electric power quality is the degree to which the voltage, frequency, and waveform of a power supply system conform to established specifications.

Good power quality can be defined as a steady supply voltage that stays within the prescribed range, steady AC frequency close to the rated value, and smooth voltage curve waveform (resembles a sine wave).

Deficient power quality would begin to harm the electrical devices and power distribution elements as frequency variations would cause processes in undesired areas.

The different power quality problems have been discussed:

Harmonics

Harmonic distortions are the major power quality issue that is considered in grid-connected PV system operations.

Harmonics are unwanted higher frequencies superimposed on the fundamental waveform creating a distorted wave pattern, nature of harmonic currents.

Harmonic frequencies are essential multiples of a fundamental frequency.

The main reason for harmonics in grid-tied systems is the existing power electronic mechanism in the PV System.

Conversion from Direct Current to Alternating current through inverters; infuse voltage and current harmonic into the system thereby resulting in power quality issues.

Such a phenomenon causes overheating in transformers and capacitor banks, making the system more and more unstable and unreliable.

Voltage Variation

The primary cause of voltage variations with grid integrated PV systems is the intermittent nature of solar irradiance.

Uneven solar irradiance is due to transitory clouds and other environmental conditions.

All these parameters lead the PV system towards unsteadiness via a course of voltage variations.

Uneven voltage variation leads to Voltage Sag and Swell and short and long interruption.

When the supply voltage falls for a short time, it is called Voltage sag (voltage falls in the magnitude range of 10% -90% of the RMS voltage).

When the supply voltage increases for a short time, it is called a Voltage swell (voltage increases beyond 110% of the RMS voltage).

Short and Long Interruptions: Interruption is defined as the decrease in the voltage supply level to less than 10% of nominal for up to one-minute duration is called voltage interruption.

If the interruption occurs for less than one minute, it is defined as a short interruption whereas if the time duration is higher than one minute, it is said to belong to interruption.

However, the term "interruption" is generally used to refer to short interruption, while the latter is headed by the word "sustained" to indicate a long-duration or long Interruption.

Reactive Power

Very Often, a Photovoltaic system is intended to work near the unity power factor, so that it can utilize maximum solar energy.

With this instance, the electrical grid gets real power from a Photovoltaic system that will adjust the outflow of reactive power in the PV system.

Hence, close-by busses voltage will be improved because of deficient reactive power.

Throughout the action, the system's usual power outflow may have undesirable results owing to deficient reactive power.

This may reduce the power that entails deficient transmission.

Frequency Variation

Frequency variation (fluctuation) is a variation from the standard nominal value (typically 50 or 60Hz) of power system frequency.

Frequency variation over tolerance value (+/-5%) is not well for the PV system and may direct the system to collapse.

In a Photovoltaic system, frequency variation depends on climatic conditions, weather, and topographic position which can cause severe troubles.

Scarcity of Materials for PV Cells

The silicon solar cells that currently dominate the world market suffer from three fundamental limitations.

A promising new way of making high-efficiency solar cells, using Perovskites instead of silicon, could address all three at once and supercharge the production of electricity from sunlight.

The first major limitation of silicon photovoltaic (PV) cells is that they are made from a material that is rarely found in nature in the pure, elemental form needed.

While there is no shortage of silicon in the form of silicon dioxide (beach sand), it takes tremendous amounts of energy to get rid of the oxygen attached to it.

Typically, manufacturers melt silicon dioxide at 1500-2000 degrees Celsius in an electrode arc furnace.

The energy needed to run such furnaces sets a fundamental lower limit on the production cost of silicon PV cells and also adds to the emissions of greenhouse gases from their manufacture.

Certain solar technologies require rare materials in their production.

This, however, is primarily a problem for PV technology rather than CSP technology.

Also, it is not so much a lack of known reserves as much as current production cannot meet future demand: Many of the rare materials are byproducts of other processes rather than the focus of targeted mining efforts.

Environmental Impact

Although pollution related to solar energy systems is far less compared to other sources of energy, solar energy can be associated with pollution.

Transportation and installation of solar systems have been associated with the emission of greenhouse gases.

The one environmental downside to solar technology is that it contains many of the same hazardous materials as electronics.

As solar becomes a more popular energy source, the problem of disposing of hazardous waste becomes an additional challenge.

However, assuming the challenge of proper disposal is met, the reduced greenhouse gas emissions that solar energy offers make it an attractive alternative to fossil fuels in the upcoming future.

However, some toxic materials and chemicals are used to make photovoltaic (PV) cells that convert sunlight into electricity.

Some solar thermal systems use potentially hazardous fluids to transfer heat.

Leaks of these materials could be harmful to the environment.

U.S.

environmental laws regulate the use and disposal of these types of materials.

As with any type of power plant, large Solar Power plants can affect the environment near their locations.

Clearing land for construction and the placement of the power plant may have long-term effects on the habitats of native plants and animals.

Some Solar Power plants may require water for cleaning solar collectors and concentrators or for cooling turbine generators.

Using large volumes of groundwater or surface water for cleaning collectors in some arid locations may affect the ecosystems that depend on these water resources.

In addition, the beam of concentrated sunlight a Solar Power tower creates can kill birds and insects that fly into the beam.

Nevertheless, solar energy pollutes far less than other alternative energy sources.