EMMA EXPORT CONTROL
Mcgarritys Quarry supplies stone sand and concrete to the surrounding area. The quarry has high demand during the day when the quarry is in full operation with various industrial sized equipment drawing vast amounts of energy. The quarry owners installed a Vestas 225 Wind turbine to help reduce the electricity bills but also to be a greener cleaner company. The turbine is also able to provide vast amounts of energy but this is somewhat mismatched to the demand on site.
The Problem – The site connection is curtailed to zero export due to the connection constraint imposed by NIE. The site has a zero export G59 relay which cuts out the turbine whenever it exports any power. Due to the mismatch in production to demand the turbine tripped out frequently during normal working hours where the production was greater than the demand for brief periods. After 6pm the site loads drop to a very low background usage leading to the turbine tripping out continuously due to over export on the zero export G59 relay.
Issues arising from turbine dropouts.
The main issue with the shutdowns is financial return but this is calculated based on costs, savings and earnings.
Issue 1 costs – While the Vestas the turbine is a very robust and well proven machine; shutting it down frequently (multiple times per day) due to over export disconnects is mechanically strenuous on the turbine. This particular install had the turbine manually switched on in the morning when the Quarry opened and off in the evening at home time. This leads to accelerated brake wear and mechanical wear and tear increasing maintenance costs.
Issue 2 costs – The turbine is expected to offset the electricity costs on site when it is producing power. If the turbine is producing more power than is being used at any point it would turn off on an over export event. This means that while the wind is more than sufficient to offset the electricity costs it can’t continue to run meaning that the clients predicted savings will not be as expected.
Issue 3 earnings – The ROC’s to be earned off this installation are a fraction of what they could be if the turbine was allowed to run at its full potential all the time. As the machine was only on during working hours it means that it only had the potential to generate during the working week which is less than 50% of its potential.
The quarry M&E contractors Axon Power engaged with Cool Power Products to design a solution to prevent the turbine from the various issues associated with a zero export connection.
Along with doing its job of preventing export; EMMA also provides temperature feedback which helps govern pumps and valves on site based on water temperature. This is achieved using the store dump feature in the EMMA system. There are three temperature settings on this system each providing control to a different valve or pump to maintain a safe temperature in the various tanks used to store the hot water at different temperatures.Objective – The EMMA solution needed to manage all the exportable power and use it on site preventing any export so the turbine would stay on line as its core objective
Versatility – The EMMA solution needed to be flexible so it could be increased in size in the future for further addition of generation. This comes as standard with the EMMA Ehub system meaning that up to 18kW chunks of extra load can be added to each phase with each Ehub providing > 1.5MW scalability. The containerized unit left extra space for more cabinet additions and the existing cabinet system left extra space for 3 more Ehubs with 54kW of additional load available to be installed.
The EMMA solution needed to be flexible so it could be increased in size in the future for further addition of generation. This comes as standard with the EMMA Ehub system meaning that up to 18kW chunks of extra load can be added to each phase with each Ehub providing > 1.5MW scalability. The containerized unit left extra space for more cabinet additions and the existing cabinet system left extra space for 3 more Ehubs with 54kW of additional load available to be installed.
Hotwater usage – The client had a definite plan for the extra power which was going to be converted to hot water. The client had already seen where they could save and generate money with the use of heat in the quarry aside from ROC’s earnings by using it:
1) To increase the temperature of the wash-down water for the drivers to clean the lorries once they return from a pour keeping the lorries clean and presenting a professional image of the company.
2) To heat the working area where the workers are manufacturing the concrete slats meaning that free stored heat from excess generation could be used without importing power to heat the area like a battery.
3) To be used for providing heat to the hood which sits above the slats to improve/speed up the curing process for the concrete
Visibility – The client was never aware of what his power profile was but wanted to be able to observe this in real time. The Epro system provides monitoring of each phase individually and also a total of the three phases combined output. This monitors the total generation of the turbine, the import from and export to the grid and also the demand of the site at any given time. The logs also display how much power is sent to the tank. The power sent to the tank is an accurate indication of how much power would have been exported or lost in this case where the turbine would have had to shut down. It also allows the client to see what power is available if they want to put in battery storage in the future. In this case the battery storage can be sized based on average available energy over a 24-hour period versus the import over the same period. Armed with this information over a year an accurate economical battery storage size can be arrived at to help reduce import even more. This information is uploaded to the CoolPower Products Database so the client can easily look through at any given time to make sure all is well with the turbine and the system is continuing to save money on his bills. grid for little to no payback.
Taking a closer look at the EPRO in action it is evident how flat and stable the import in red and export in blue are in a volitile period of high wind. While the turbine is set on the lower gear in this log with a rated max output of 150kW it is clear that the machine is generating close to 180kW if you multiply the generation green line by 3. For this Cool power products were able to advise at the pricing stage that the system should be oversized having past experience with the same make of turbine. The purple line is the EMMA controlling the heat to the tank in line with the generation and the background load.
Justification- On just one phase it is clear that the EPRO system has stored 27947kWh of electricity into heat on site with phase 2 and 3 having similar storage adding up to 85000kWh stored in heat over a 6 month period. It is safe to assume that the turbine over the course of a year would missed out on producing 150,000kWh minimum with out the EPRO system in place not to mention the amount of service fee’s and brake changes that have been avoided from the turbine being halted on a daily basis due to over export.