According Match now quote their solar panels as

According
to Energy UK, over 54% of the UK’s electricity was produced from fossil fuels in
2016 – 42% from natural gas, 9% from coal and 3.1% from other sourcesi.

However, burning these fossil fuels creates dangerous greenhouse gases, such as
carbon dioxide, which damages the atmosphere and contributes towards global
warming. This in itself makes fossil fuels an inconvenient source of energy, but
when coupled with the prediction that fossil fuels will run out by the end of
the centuryii,
it becomes clear why it is vital that we explore alternative energy sources. So,
what are our potential options for energy in the future?  Solar
PanelsOur
future energy sources would ideally be renewable, meaning they will never run
out, unlike fossil fuels which are unrenewable. One of the best renewable
sources of energy is the sun, whose energy can be captured and collected using
solar panels. A solar panel is a large collection of small solar cells. The
idea of using a solar panel to collect energy is based on the photovoltaic
effect, which was first observed by father and son Antoine-César and
Alexandre-Edmond Becquerel in 1839iii.

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This is the idea that a potential difference can be created between two
materials when light is incident upon it. This phenomenon was studied heavily
throughout the mid 19th century, which lead to the creation of the
first solar cell by American inventor Charles Fritts in 1883iv.

Fritts’ cell was made from of a layer of selenium covered with a thin film of
gold. Although this was a monumental discovery, it wasn’t deemed a viable
energy source due to its efficiency of <1%.However, with advances in technology, solar panels are now a much more suitable method of producing electricity. Green Match now quote their solar panels as delivering between 15%-22% efficiencyv, which is still lower than the average efficiency of producing electricity from fossil fuels (around 36%vi), but substantially greater than Fritts' cell. Modern day solar panels are made up of many individual photovoltaic cells. Each cell is made from two layers of semi-conducting silicon. The top layer is seeded with phosphorus, giving it extra electrons and hence a negative charge. The bottom layer is seeded with boron, which gives it a positive chargevii.

A depletion layer is sandwiched in between these two silicon layers, which
disallows the flow of electrons between the two silicon layers. This depletion
layer helps each layer to retain its positive/negative charge, or else
electrons would simply jump from the negative layer to the positive layer to
balance out the charge. When photons from the sun hit the negatively charged silicon,
the electrons can gain enough energy to escape the silicon via the
photoelectric effect. Electrical conductors are attached to each layer of
silicon so that the free electrons can travel through the conductor, around a
circuit, and back into the positive layer to complete the circuitviii.

This is how a solar cell can produce an electric current when under sunlight.  Wind
TurbinesAnother
renewable energy source is wind. Wind turbines can harness the wind to produce
electricity. Humans have used wind energy for thousands of years, such as for
propelling boats, but they’ve only been used for generating electricity since
1887 when Prof James Blyth created the world’s first known wind turbine in
Scotlandix.

Modern day wind turbines still work in a similar way. As air passes through the
blades of the turbine, it causes it to rotate. This rotation turns an
electrical generator, inducing an electric current in the traditional way. The
generated electricity travels from the generator to a step-up transformer,
which then transports the electricity at a high voltage, yet low current, to
where it’s needed. It
is quite simple to calculate the power generated by a wind turbinex.

The kinetic energy, KE, of any mass, m, with velocity, v, can be calculated by:

Equation
(1)

 

 

 And
the rate of mass flow can be given by:

Equation
(2)

 

 

 The
rate of change of energy, or power, of the wind can be given by:

Equation
(3)

 

 

 By
substituting Equation (2) into Equation (3), it can be found that:

Equation
(4)

 

 

 However,
it is not possible for a wind turbine to capture all of this power from the
wind. A power coefficient, Cp,
can be factored into the equation:  The
value of this coefficient varies from turbine to turbine, but it can never be
above 0.59 due to Betz’s Lawxi.

The value of Cp usually
lies around 0.35-0.45x.  Nuclear
PowerThere
are two process in which nuclear power can be produced – fission and fusion.

Nuclear fission is already in use in the UK, accounting for 21% of electricity produced
in 2016i.

Fission involves the splitting of uranium-235 into a variety of smaller
daughter nuclei. This is done by firing a slow-moving neutron at the uranium
nucleus, which causes the nucleus to become so unstable that it splits into
daughter nuclei and some more neutrons. Below is a possible fission equation:  This
uranium nucleus is composed of 92 protons and 143 neutrons. In terms of atomic
mass units, these constituent parts of the nucleus have a total mass of (92 x
1.00728) + (143 x 1.00866) = 236.90814 u (where 1 u = 1.661 x 10-27
kg). However, its actual isotopic mass is only 235.04393 uxii.

This difference is due to something called binding energy. When all the protons
and neutrons are separate, they do indeed have a combined mass of 236.90814 u.

When these nucleons are brought together to be bound into a nucleus, they
become more stable, and consequently release energy. The energy released is the
binding energy. According to Einstein’s E=mc2,
when the nucleons lose energy, they also lose mass. This is what causes the
mass of a uranium-235 nucleus to be less than the combined mass of its
constituent parts. Looking
back at the equation, the total mass of the reactants is 236.05259 u, whilst
the final mass of the products is 235.85328 u. This means the mass lost during
this reaction 0.19931 u, which equates to 2.98 x 10-11 J, or around 186
MeV. This is an incredibly large amount of energy considering it’s from just
one nucleus. Considering just one gram of pure uranium-235 would contain around
2.56 x 1021 nuclei, this gram could produce over 76 GJ of energy. In general, a nuclear reaction
will produce energy if the binding energy per nucleon of the products is
greater than that of the reactants. You can imagine the above equation in two
steps. Energy must be put in to break the uranium nucleus up into its
constituent nucleons, equal to its total binding energy. Energy is then
released when these nucleons recombine to form the daughter nuclei. This
process does not actually happen, it just makes it easier to consider the
energy changes. There must be the same number of nucleons on each side of the
equation, as protons and neutrons can’t just disappear. The binding energy per
nucleon of uranium is less than that of tin and molybdenum. Therefore, less
energy is put in when breaking up the uranium than is released when the Sn and
Mo nuclei are formed. This explains why, overall, energy is released, and the
mass decreases.  A
similar explanation can be applied to nuclear fusion. Contrary to fission, fusion
involves fusing together two small nuclei to produce a larger nucleus. The most
common reaction for nuclear fusion involves reacting deuterium (hydrogen-2) and
tritium (hydrogen-3) to produce helium-4 and a neutron. Again, as helium has a
higher binding energy per nucleon than the hydrogen nuclei, energy is released
during this process. To look at it quantitatively, this reaction causes a mass
of 0.01889 to be lost, which is equivalent to 2.82 x 10-12 J, or
17.6 MeV. As one gram of hydrogen (which is 50% deuterium and 50% tritium)
would contain around 2.41 x 1023 nuclei, this one gram sample could
theoretically produce 679 GJ of energy.  Which
is the best method?Enough
solar energy is incident on the Earth every hour to meet the energy needs for
an entire yearxiii.

Of course, this is assuming the entire world was covered with 100% efficient
solar panels, but it does show the huge potential of using the sun as a source
of energy. We only need to capture ~0.01% of the sun’s energy to
continuously power the entire world. An average onshore wind turbine will
produce around 6 million kWh in a year, which is enough to provide electricity
for 1,500 average EU householdsxiv.

Nuclear fission already supplies around a fifth of the UK’s energy, and this is
expected to rise to a third by 2035xv.

This shows that all three methods have their merits. Furthermore, none of these
methods release greenhouse gases, so are much better for the environment than
burning fossil fuels. However,
whereas solar and wind are renewable, sustainable sources of energy, the
reactants required for nuclear energy production are limited, but they will
still last for the foreseeable future. Another downfall of nuclear is that it
does produce radioactive waste products. These can be harmful to the
environment and wildlife, as well as human life, so has to be stored carefully
for a long period of time. The
drawbacks of solar and wind energy are that they’re not always available. A
solar panel cannot produce electricity when it’s not sunny, and wind turbines
will only work at wind speeds of around 5-25 ms-1xiv