Past papers Flashcards
What is the conversion factor for Celsius and Fahrenheit?
Fahrenheit = (Celsius x 1.8) + 32
What are the three main issues for commercial algal production?
Maintaining desirable species
Low yield of oil
High cost of harvesting
How can issues with algae production be overcome?
Increasing algae oil content
Increasing growth rate
Robust growth systems
Coproduction
Increasing oil extraction efficiency
What is the average algae production of an open pond?
5-10g/m2-day
What is the average algae production of an enclosed bioreactor?
2-3g/L-day
List four carbon capture technologies
Post combustion capture
Direct air capture
Blue hydrogen
BECCS
How big is a hectare?
10,000m2
What is the power coefficient Cp of a wind turbine?
The fraction of available wind power in an area that is actually generated by a turbine
Why does the stream tube of a wind turbine expand after passing through?
The mass flow rate must be maintained due to conservation of momentum
What is the theoretical relationship between wind turbine radius and output power?
Power is proportional to area so it is proportional to radius squared
What is a litre in m3?
0.001m3
What is a watt?
1 joule per second
Why is 100% efficiency of a wind turbine impossible?
It would require the wind to have a speed of zero after passing the turbine
How to you find required fuel when given power output and efficiency?
Divide output by efficiency for max potential then divide this by energy content of the fuel
What is the reflectance of a material at the boundary between materials with refractive indexes of n1 and n2?
((n1-n2)/(n1+n2))^2
What material is best for PV where low weight, low size and high efficiency are needed?
Gallium Arsenide
What is the most commonly used type of photovoltaic cell?
Polycrystalline silicon
What are the benefits and drawbacks of a perovskite PV cell?
Cheap
Efficiency close to silicon
Short lifespan
What are the benefits and drawbacks of an indium phosphide PV cell?
Potentially the highest electrical output
High material cost
Not at optimum efficiency
Summarise the generations of biofuel
Produced from food crops
Growing on land where food cannot be grown
Derived from algae
Derived from genetically engineered microorganisms
What are the benefits and drawbacks of a cadmium telluride PV cell?
Thin film application
Cheapest per W
Low efficiency compared to Si
If asked for the environmental impacts of a renewable scheme, what can you always include?
The fact that it is a renewable technology that leads to lower carbon emissions
What can be an ethical benefit of a new power source in a country that currently imports power?
Improved energy supply security
What are some negative impacts of building a solar farm?
Land area use displaces wildlife and crops
Rare Earth element mining is destructive and materials are toxic
