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Self sufficiency and energy independence
We are all being subjected to the effects of corona based hysteria and as a result interest in self sufficiency and energy independence has increased substantially. The ability to utilize the sun’s virtually infinite energy in conjunction with well designed energy storage systems allows residential and commercial customers alike to wrench back some element of control. A site's consumption can now be addressed by the grid, solar, energy storage or all three at different times.
So what are we actually talking about with renewable and energy storage on the grid?
There are two aspects; tariff optimization and emergency backup.
With tariff optimization the site's energy consumption whilst the grid is intact is addressed by the three sources as mentioned previously:
- Energy storage
Based on load profile- how much you are consuming and when- the “ brains” of the system, let's call it the Total Energy Management System (T.E.M.S) determines what of the three sources takes the lead.
For example, we have a factory or residence with electrical loads during daylight hours and these loads are addressed directly by the solar.
If the loads are greater than the solar can provide at that point in time, then the shortfall is addressed by either of the other two sources.
If the solar output is greater than the loads the excess energy flows to the battery or to the grid.
As we are dealing with the grid we may have a tariff system where the cost of energy can differ depending on the time of day and day of the week, for example peak and off peak tariffs. This coupled with the difference between the cost of bringing energy into the site and the cost allocated to energy flowing from the site means a well designed system must take this all into account.
For example, let's say that the cost of grid energy from 7am - 11pm, Monday to Friday is:
- $0.30/kWh but between 11pm - 7am
- Weekends the cost is $0.15/kWh
- Any excess solar produced energy that escapes to the grid is paid out at $0.07 kWh.
So ideally you would aim to minimize the excessive energy flowing out to the grid.
Don’t get me wrong! $0.07/kWh is better than zero dollars but wouldn’t it be preferable that the excess goes into a battery storage system that can be “drawn upon” in conjunction with the solar to save that peak energy value of, in this case, $0.30 kWh?
Peak and off peak tariffs
Also the cost discrepancy between the peak tariff and off peak tariff dollar value can be utilized to charge the batteries during months of low solar gain.
In other words charge the batteries during certain times then discharge those same batteries when energy is at its highest cost!
This is the T.E.M.S. approach.
There is an interdependence between all the factors;
- Cost of energy
- When the solar actually produces electricity,
- How much you consume on site and when
- Storage capacity
- When the storage accepts energy
- When the storage releases energy and the grid.
When thinking of energy storage on the grid most people automatically think of battery backup. In other words if the grid fails there is still power but this is not always the case.
Some energy storage systems out there are simply designed for tariff optimisation, i.e. they only work when the grid is working.
Time and time again we hear stories of customers paying for a supposedly well designed system with the expectation that the site would have power if the grid failed but no!
The ability to service loads during a grid outage is most important for many reasons; maintain machinery, essential loads, lighting, security, internet, refrigeration etc. When designing a T.E.M.S with both tariff optimization and emergency backup functionality there is a balancing act with the energy storage’s role.
Emergency backup and tariff optimization
For example a customer has requested full site backup and tariff optimization. The question is how much actual capacity to allocate between the required functions?
The answer is tempered by the fact that a grid outage may happen at any time, day or night. If, for example, the outage occurs during daylight hours with the sun shining and the energy storage system at near full capacity the owner can be confident that site loads will be serviced for x amount of time.
But if grid outage occurred in the evening then batteries will be the sole source and they may have taken a “flogging” during the day.
This is where the EB:TO ratio is most important (Emergency Backup to Tariff Optimisation storage ratio).Too much storage allocated to T.O. means reduced ability to service loads outside of daylight hours via E.B.
Conversely, too much storage allocated to E.B. means a wasted asset in regards to the energy storage system contribution to T.O. Basically damned if you do and damned if you don’t.
All energy consumption has to be looked at from the perspective of a T.E.M.S. (Total Energy Management System) approach.
A customer’s expectations in regards to system performance and functionality is tempered by many factors and it is vitally important that the system designer understands the intrinsic connections between the three sources on the one hand and the site’s individual characteristics. With a well designed system that has taken all the above into consideration the customer can now experience an increased level of self reliance and control.
If you’d like to see what Greenwood Solutions get up to in the real world of renewable energy, solar, battery storage and grid protection check out our industry and commercial pages: