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Advanced super capacitor-based storage

Telecommunication, Wireless

Energy Imbalance Market Solution

communication-tower

Statement of Utility Problem:

Balancing Authorities (BAs) hold reserves to balance discrepancies between forecasted and actual load within the operating hour. These “flexibility” reserves are in addition to the spinning and supplemental reserves carried against generation or transmission system contingencies.


Flexibility reserves generally fall into two categories: regulation reserves automatically respond to control signals or changes in system frequency on a time scale of a few cycles (one cycle is 16.7 mS) up to five minutes, while load following reserves provide ramping capability to meet changes in net loads between a 5-minute and hourly timescale.


Higher penetration of wind and solar energy increases the amount of regulation, load following and spinning reserves needed to accommodate the uncertainty and variability inherent in these resources while maintaining acceptable balancing area control performance. By pooling load and resource variability across space and time, total variability can be reduced, decreasing the amount of flexibility reserves required to ensure reliable operations. This reduces operating costs by requiring fewer thermal generators to be committed and operated at less efficient set points.


While there is currently no defined requirement for BAs to carry load following reserves, all BAs must carry load following reserves in order to maintain control performance standards within acceptable bounds, and reserve requirements will grow under higher renewable penetration scenarios.


Transmission transfer capability limits between BAs will constrain EIM benefits. These limits can be physical or contractual. If the transmission paths connecting two BAs are congested, generators in BA-1 will not be able to provide additional imbalance energy to BA-2, and vice versa.  BA-1 and BA-2 typically anticipate initially relying on BA-1 transmission contract rights to BA-2 to facilitate EIM transactions, as opposed to a “flow-based” transmission optimization, similar to those in use in organized energy markets, that would be unconstrained by contract limitations.


Due to ramping rates of thermal generation units, they are unsuitable for dispatch to meet regulation requirements and typically are not included in an EIM solution.  Each BA therefore keeps its regulation units operating within their territory for this purpose at a very high cost due to their low efficiency operation.


Cell Tower Owner Opportunity:

Cell tower owners such as AT&T, Verizon and T-Mobile generally install backup generation at sites to ensure continuous operation should there be a disruption to the electric service.  These backup generators can cost up to $100,000 per site along with annual maintenance requirements, are seldom needed to operate and provide no alternative use.  Drawbacks of stand-alone generators also include CO2 emissions which contribute to global warming. With a switch to a green energy storage solution, there is an opportunity for these owners to participate in the Energy Imbalance Market providing Flexibility reserves thereby creating a revenue stream for these backup resources.


SuperCap Energy and Intelligent Design Solar Integrated Solution:

Where the EIM falls short in providing Flexibility reserves and locational constraint limitations, the Supercap Energy Storage and Vertiv rectifiers positioned within these BAs, at cell tower locations, can provide the needed resources as an adjunct to the communication company’s need for backup power resources. Rather than have a backup generator on standby which provides no economic benefit, the Supercap Energy solution will provide a continuous revenue stream by supplying Flexibility reserves in the EIM 5-minute load following and instantaneous regulation markets. These otherwise underutilized resources will provide a substantial revenue stream to the owners while meeting their backup power requirements.


Intelligent Design Solar will provide the needed highspeed bi-directional control, encrypted communications, and data storage to integrate these resources into the EIM control systems of the BAs. IDS historical data reserves will provide significant value for analysis purposes and determination of additional resource requirements and billing settlement in the BA service area. Both dispatch for load regulation and instantaneous frequency control would be managed by the IDS local processor in communication with the central IDS Concentrator and BA’s SCADA control system.



Market Proof of Concept:

The state of Hawaii has enacted legislation that requires all electricity come from renewable resources by no later than 2045.  Consequently, a significant effort is being put forth by the Hawaiian Utilities, HECO on Oahu, MECO on Maui and HELCO on the big island of Hawaii, to install larger amounts of solar and wind resources.  As stated earlier renewable energy resources only exacerbate the EIM needs.


A testbed could be established in a miniature version of the EIM market on one of the Hawaiian Islands.  Complexities of the EIM are significantly smaller in the restricted area of a non-interconnected island and those resources are more valuable due to the higher variability in a confined resource pool.  In other words while the problem is simpler because only one BA exists, the operational integrity of the electric grid is inherently more unstable because it is smaller and each renewable resource has a higher impact on system stability.


A potential exists to support the smaller grid stability by introducing distributed Super Cap energy storage. The approximately 25 Verizon cell sites on the Big Island are capable of hosting 250kW of Super Caps each for a total of 6.25 MW of EIM capacity to supply regulation and load balancing needs.  Strategic location of resources at these distributed sites would mitigate any transmission congestion issues and demonstrate the potential for this solution’s application in a larger Western US market comprised of dozens of BAs.


Revenue Potential:

Flexibility reserves are made up of regulation and load following reserves. Typically, the ratio is 20% regulation (instantaneous dispatch) and 80% load following (5-minute market).


With respect to the load following requirement, here is a rough estimate based on known information from the California market. CA ISO had a Peak demand of 45,486 MW in 2009. Hawaiian Electric Light Company’s 2018 Peak was 190.8 MW. The savings in CA from EIM in 2009 was $105 million. To estimate the benefit for HELCO the following equation is applied:

HELCO 2018 savings = CAISO 2019 savings X HELCO 2018 peak MW / CAISO 2009 peak MW

HELCO 2018 savings = 105 million x 190.8 MW / 45,486 MW = $440,443.


Because there is no interconnection between islands, each utility HECO, MECO and HELCO must maintain much higher reserve margins to protect against generation resource loss. HELCO maintains a 26.9% generation reserve. As more renewable energy resources are introduced to the islands, greater reserves will be required. A portion of spinning reserves can be supplied by Super Caps.


A 6.25 MW installation provides a potential 3.3% regulation capability and displaces 12% of the generation reserve being used for load following.  Remaining within the Supercap Energy warranty performance requirements, the Super Cap can be completely discharged four times/day at a rate of 1C, or 74 Amps. Such a use would provide unlimited incremental regulation capability for an 80% charged Super Cap since this use would be small, rapid up and down charge/discharge cycles in the range of 17 mS to one second. In one second at 74 Amps, is a discharge/charge of 0.02 Amps, or 1 Watt/second per Super Cap. With 6.25 MW, there would be 1760 Super Caps in operation. Their instantaneous capability @ 1C-rate would be approx. 1.8 kW/second.


6.25 MW of Super Cap capacity and energy would cost approx. $5,312,500 for Super Cap storage and $3,740,000 for Energy Server capacity. Total installation cost of approx. $10 million (including labor). $10 million/6,250 kWh = $1,600/kWh.


NPV on a 45-year life solution is approx. $22 million assuming 1% annual inflation rate and 2% value growth rate (need and value increase as Hawaii Electric moves toward 100% renewable in 2045).


Additional benefits to the utility are to be determined.  We don’t know how much regulation they have continually running that can be displaced and at what cost.  We also don’t know how the provision of this new Flexible regulation resource will delay replacement and other expenses related to their fossil fleet.  Finally, due to the increasing reliance on renewable energy resources, the value of the new capability will grow over time.  How much is unknown without input from the utility.

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