Question

Question 1
a) Continuing concerns about the ‘sustainability’ of both fossil and nuclear fuel use
have been a major catalyst of renewed interest in the renewable energy sources
in recent decades. One of the criteria of renewable energy source is it does
not entail significant pollutant emission or other environmental problems.
i) Based on this criterion and solar photovoltaic panel life cycle (from raw
material extraction, manufacturing to disposal), discuss the sustainability of
solar photovoltaic panels.
ii) On a large scale, compare the sustainability between wind energy and solar
energy (PV panels).

b) Consider a horizontal axis aero-generator that designed to develop 100 W
(electrical power) at a wind speed of 7 m/s. NACA 4412 airfoil is used for the wind
rotor blade and the design power coefficient is close to the maximum value of
commercial small wind turbine. The combined drive train and generator efficiency
is 0.9. Assume the air density to be 1.224 kg/m3.
i) Suggest the number of rotor blade. Provide the reasons for the blade
number selected.
ii) Estimate the power coefficient. Calculate the wind rotor radius.

c) One of the elements considered in energy efficient buildings is high performing building envelope. Determine 2 parts of building envelope that applicable to a single-storey house in Malaysia.

Answer 1

​​​​​​a) i) Although it seems that solar energy is a perfectly sustainable and green source of energy but taking a closer look reveals the entire picture.

Producing photovoltaic panels requires minerals like copper, nickel, and cadmium. For instance, if we think of silver, its supply and demand for photovoltaic purposes are, respectively, ~ 27 billion kg and 242 million kg (in 2017). Other minerals such as lithium or silicon are also at risk of having a demand that outstrips supply today and in the future.The problem here isn’t really about these minerals being finite resources because there are still many reserves. It is about the mining activities themselves. Indeed, the extraction and the chemical separation processes to get these minerals is very polluting and in many places toxic waste is not responsibly taken care of. Together with other impacts like soil erosion or mercury contamination, mining activities can pollute the air, water, and soils and harm local biodiversity and populations. The mitigation of these and other risks depend on the local sites’ governance practices.

Fabricating the panels requires caustic chemicals such as sodium hydroxide and hydrofluoric acid, and the process uses water as well as electricity, the production of which emits greenhouse gases. It also creates waste. These problems could undercut solar's ability to fight climate change and reduce environmental toxics.

ii) Both depend on often volatile forces of nature, but overall, solar panels provide more consistent energy. Solar panels don't include moving components, as wind production units do. These and other differences play important roles in deciding which renewable energy option is best for you.

Solar panels are quite expensive to manufacture not to mention the disposal problems and the raw materials mining.Also it is appropriate only for plases that receive a good amount of sunlight.The efficiency of the panels is also quite less and it depends a lot on the orientation of the panels with respect to the sun light.But there are some advantages of solar panels.

They don't have moving parts and can be installed anywhere like the roof of our house.They can be directly connected to the main circuit of the house.

Coming to wind energy, there are a lot of limitations.They can be only built in windy places .They require a lot of space and money and the moving parts can malfunction .They can also be death traps for birds.

However some benefits of wind energy over solar energy is that they can operate at night also.Their efficiency is more than the solar panels.They don't require minerals so no mining.They are almost entirely eco-friendly.

b) i)My suggestion would be three blades. Two blades would offer greater energy yield than three, but would come with its own issues. Two-bladed wind turbines are more prone to a phenomenon known as gyroscopic precession, resulting in a wobbling. Naturally, this wobbling would create further stability issues for the turbine as a whole. This would also place stress on the component parts of the turbine, causing it to wear down over time and become steadily less effective.

Any number of blades greater than three would create greater wind resistance, slowing the generation of electricity and thus becoming less efficient than a three blade turbine.

b) ii)