Renewable Energy Flashcards

Flashcards covering economics of storage, thermal energy storage, electrochemical energy storage, introduction to energy flexibility, bioenergy, geothermal energy, heat pumps, hydroelectric power, tidal power, and wave power.

What are examples of short storage durations (seconds)?

Electrical/electrochemical, mechanical (e.g. flywheel)

What are examples of long durations (days up to interseasonal) storage categories?

Chemical e.g. hydrogen, pumped hydro power, large-scale thermal (potentially underground)

What are the three key thermal energy storage mechanisms?

Sensible heat, Latent heat, Thermochemical reactions

What is sensible heat thermal energy storage associated with?

Heating and cooling of the active material

What is latent heat thermal energy storage associated with?

Phase changes of the active compound between solid, liquid, and gaseous states.

With what process is thermochemical storage associated?

Reversible chemical reactions that absorb or release thermal energy

What do energy and power investment costs (specific) refer to?

Cost to add energy and power capacity, respectively, covering all costs to set up the storage system.

What does construction time refer to in the context of energy storage economics?

Time to construct the storage system, from breaking ground to being operational.

What does replacement cost refer to in the context of energy storage economics?

Cost to replace major components beyond standard O&M costs.

What is the replacement interval in the context of energy storage economics?

Time interval for replacement of major technology components.

What does O&M cost refer to in the context of energy storage economics?

Cost to operate, insure, and service major components, possibly scaling with energy discharged or power capacity.

What is charging cost in the context of energy storage economics?

Cost to charge the storage device, accounting for the amount of energy used during charging and its price.

What does End of life cost refer to in the context of energy storage economics?

Cost to dispose of or decommission the system at the end of its life, which may be positive or negative.

What is the discount rate in the context of energy storage economics?

Rate at which to discount future costs and revenues, based on the cost of raising capital or a hurdle rate.

What does levelized cost of storage (LCOS) quantify?

Quantifies the overall cost per unit of discharged energy for a given technology and situation.

What does annuitized capacity cost (ACC) quantify?

Quantifies the overall cost per unit of discharge energy, focusing on power rather than energy.

What are sealed batteries?

Electrodes (active materials) separated by an ion-conducting electrolyte.

What are flow batteries?

Two liquid electrolytes circulated and stored outside the system.

What are the components of Lead-acid batteries?

Sponge-like anode of powdered lead (Pb), cathode of powdered lead dioxide (PbO2), and electrolyte of aqueous sulphuric acid (H2SO4).

How do Li-ion batteries generate current?

Movement of Lithium ions (Li+) from anode (+ve charge) to cathode (-ve charge) during discharging.

How do Vanadium redox-flow batteries operate?

Electrolytes stored in external tanks and pumped into cell as required.

What do Supercapacitors provide?

Very large amount of power for a short period; ions not intercalated into electrode.

How can hydrogen be produced?

Electrolysis of water (H2O) separates water into hydrogen (H2) and oxygen (O2).

What challenges does balancing demand and supply address?

Frequency balancing, diurnal peaks, wind droughts, and interseasonal imbalances

What flexibility options exist for energy systems?

Flexible generation, network interconnection, demand side response, and (electrical) energy storage.

What forms of energy are active in mechanical energy storage?

Pumped hydropower (gravitational potential) and flywheels (kinetic).

How does Compressed air energy storage (CAES) function?

Storing energy by compressing and decompressing the working fluid (air).

What are the key components of CAES?

Reversible air turbine, reversible electrical generator, and a means of storing the compressed air.

What is bioenergy derived from?

Organic material that is (or was recently) alive.

What are the opposite processes governing the carbon cycle?

Photosynthesis and Combustion

What is a direct use of feedstock to end use?

Direct combustion for heat and power production.

What is the major source of geothermal energy?

Heat from the core constantly flowing to surface.

What essential features do geothermal sites have?

Aquifer containing water accessible by drilling, cap rock to contain geothermal fluid, and a heat source.

How do dry steam power plants function?

Hot steam passed directly through a turbine.

How does an Organic Rankine Cycle power plant function?

Uses a secondary working fluid (e.g. butane).

What is first step of the heat pumps cycle?

Liquid gains heat while moving through a heat exchanger (evaporator) and vaporizes.

What is second step of the heat pumps cycle?

Cold vapour enters an electrically driven compressor, raising its temperature and pressure.

What is third step of the heat pumps cycle?

Hot vapour enters a second heat exchanger (condenser) and condenses to a warm liquid, giving up heat.

How to calculate nominal power of hydroelectric plant?

Power = pressure head x volumetric flow rate

What causes the rise and fall of seas that are used in the Tidal power: barrage systems

Gravitational pull of the moon

What causes sea waves used as source in wave power systems?

Sea waves move up and down caused by wind over the surface of water

What are main wave generator types?

Fixed devices and Floating devices

What is the formula to calculate the energy stored in pumped hydropower?

Energy = mgh, where m is mass, g is gravitational acceleration, and h is height.

What is the formula to calculate the energy stored in a flywheel?

Energy = \frac{1}{2}I\omega^2, where I is the moment of inertia and \omega is the angular velocity.

What is the ideal gas law used in CAES?

PV = nRT, where P is pressure, V is volume, n is the amount of substance, R is the ideal gas constant, and T is temperature.

What is the formula to calculate the capacity of a hydroelectric plant?

Power = pressure head x volumetric flow rate

What is the formula to calculate Levelized Cost of Storage (LCOS)?

LCOS = \frac{\text{Total Costs}}{\text{Total Discharged Energy}}

How to determine discount rate?

Based on the cost of raising capital or a hurdle rate.

How is photosynthesis related to bioenergy?

Photosynthesis captures solar energy and stores it in organic material.

What is the formula of calculating equivalent annual cost?

ACC = P \times \frac{r(1+r)^n}{(1+r)^n-1}, where P is the present value, r is the interest rate, and n is the number of years.