Energy 5 Flashcards
For a 3 bladed horizontal axis wind turbine, what is the maximum power coefficient.
For a 3 bladed HAWT, maximum Cp is 49%
Why are wind turbines separated from each other by approximately 5 rotor diameters?
Minimise wake interference.
Minimise the negative effects of wake turbulence and wind shadow.
Separation allows airflow to settle down and accelerate.
What is a typical distance between adjacent wind turbines in terms of the rotor diameter?
In practice, turbines must be
separated by ~5 rotor diameters in
each direction.
Horns Rev (in Denmark) spacing between turbines is 560m (7 rotor diameters)
What the approximate value of the power density (i.e. average power output per area of land)
for onshore wind power in Ireland?
Allowing for efficiency and spacing, typical max power density per land area ~10W/m2
Due to intermittency, load factor ~22%
Actual power density ~3W/m2
In the context of wind turbine operation what is meant by the cutout speed?
The cutout speed is the wind speed at which a wind turbine’s control system or protection mechanisms intervene to shut down or limit the operation of the turbine.
This is done to prevent damage to the turbine and ensure the safety and longevity of the equipment.
Typically occurs at 25 to 30 (m/s)
What are typical weekday values for the peak and minimum demand for electricity in Ireland?
Fluctuate between a peak of the mid to high 4,000 MW to a minimum of the high 2000 MW.
State 4 strategies to match supply of grid electricity to demand.
1) modify supply (dispatchable plant/curtailment).
2) modify demand (demand side management). This can be done to a certain degree in residential homes.
3) Import/export power by inter connectors. This is the best method because Ireland has a small population.
4) Storage (long term). This is the biggest hope for renewables.
What is meant if a power source is described as “dispatchable”?
A dispatchable power source can be turned on or off at
will (from seconds to hours).
What does load following mean?
The ability of a power generation system to match its output to the changing demand for electricity in real-time.
Real time adjustments offer grid stability.
What is meant by “curtailment”?
The intentional reduction of the output of a power generation source
Often renewables, due to factors like:
oversupply
grid constraints
economic considerations
to maintain grid stability
What is the capacity of electricity interconnectors from the Isle of Ireland to Britain?
Currently 2 electricity connections from Ireland to Britain:
500MW East‐West from Rush to Shutton, Wales (EWIC)
500MW Moyle from Ballycronan (Antrim) to Auchencrosh
(Scotland)
Plans underdevelopment for 700MW link to France
Target operational date 2026
What is meant by “load levelling”?
Load leveling aims to balance electricity supply and demand over longer periods, such as days.
Ensures a more stable and consistent grid operation.
What is meant by “peak shaving”?
A strategy to reduce short term peaks in electricity demand.
Typically over minutes or hours
With the goal of minimizing the need for less efficient or more expensive peaking power plants
Helps optimize the overall efficiency and cost-effectiveness of the electricity supply system
What is the approximate cost per kWh of lithium ion batteries for utility scale storage?
$600-$2500/kWh
And $15-$100/kWh per cycle.
What does the term insolation mean?
The amount of solar radiation energy received on a surface over a specific time period, expressed in kWh/(m²·day).
It measures the solar energy available for potential power generation.
Depends on:
– Season
– Latitude
– Time of day
– Weather
