Community Microgrids Resilience
In our times when climate changes, natural disasters, planned and unplanned power outages are becoming very frequent and are a permanent fixture of our daily life, the notion of resilience is having an important place in the way living communities are defined.
Living community resilience must encompass backup power for critical community facilities such as fire stations, water, and communications infrastructure, hospitals, and emergency shelters, communal kitchens and some of the food stores, all emergency response agencies located in that area. The resilience must allow some of the community members schools, churches and so on,to evacuate in case of distress.
Living with Community Microgrids
In the best scenario, Community Microgrids can keep Community Loads online indefinitely during power outages of any nature. We account for three (load) tiers: Discretional Load, Priority Load, Critical Load most of the time called Life-Sustainable Load.
Here is how Community Loads of Community Microgrids are tailed:
Tier 1 Loads,10% of the total electric loads - are mission-critical and life-sustaining loads operational at all times.
Tier 2 Loads,15% of the total loads designated as priority loads and are maintained for a period of time when the power consumed does not encroaches over the Tier 1 power load.
Tier 3 Loads,75% of the total loads, covers all discretionary loads and is maintaining for a relatively short period of time, or for how long the Tier 1 and Tier 2 power load cumulate is not affecting the most important load carried by Tier 3.
See graphic below:
Who are the components of Community Microgrids?
There are two sides of the story: one is Behind-The-Meter (BTM), the second one is connected Front-Of-Meter (FOM) for all the consumers part of a Community Microgrid.
Behind-The-Meter or BTM has at its core local generation elements like arrays of solar panels, wind turbines, waste-to-energy, biomass and small-scale hydropower plants, but diesel generators and cogeneration facilities may also be deployed as a backup or to maximize resilience and after that all feed in BTM microgrids element.
Front-Of-Meter (FOM) is based on the transmition power lines, substations, control centers, local utility generation based on wind power, solar panels, combination solar panels methan gas in case of pick stations, only to mention the very basics of it.
Energy storage a.k.a. battery banks, can be placed on both sides, either Behind-The-Meter (BTM) or Front-Of-Meter (FOM). The placement can be done based on financial considerations for the whole community or considering special needs.
EV cars and EV transportation elements have a very active role Behind-The-Meter (BTM). EV personal cars, considering the fact battery banks associated will have a bigger energy density and a bigger capacity in the very near future, can provide so much needed energy to the household. But in case of larger park of EVs, they can be operative in a FOM scenario and balance the factor of power for the whole community at the pick time. They can act as a community energy storage unit.
Based on a Nissan Leaf 6000W battery pack, in case of a rolling blackout we can have a home critical load connected to the DC/AC converter covering following consumers:
As the name implies, community microgrids are small-scale versions of a bigger grid, except that they focus on individual power generation and distributed energy resources optimization (DER- optimization).
The main parts of microgrids:
Local generation: Solar PV panels, wind turbines, waste-to-energy, biomass, and small-scale hydropower plants may all feed into microgrids. Diesel generators and cogeneration facilities may also be deployed as a backup or to maximize resilience.
Consumption: a.k.a. ‘load’ Any type of building or structure that uses electricity is considered a load and taken into account in the demand-supply energy balance.
Energy storage: Energy storage will enable the microgrids to store excess energy in times of surplus and release it again in times of need. Electrical battery storage (e.g. batteries) being the most versatile and affordable.
Grid management system: Microgrids taking advantage of modern communications technology will have a ‘smart’ system in place that puts all resources to use in the most cost-effective and efficient way possible. When electricity demand looks ready to outstrip supply, the management system may even ‘shed’ optional loads – remotely and automatically switching off non-essential devices within households and other buildings to prevent a blackout.
Point of common coupling (PCC): This is the point at which the microgrids connect to the mains grid. A PCC is not a feature in all microgrids, but where it is it offers an extra degree of resilience, as the mains grid can be drawn on as a source of ‘backup ‘power’. Conversely, in the event of a mains grid outage, the microgrids may be able to continue to operate normally.
What are the advantages of using a Community Microgrids?
A Community Microgrids has multiple functions but we can highlight the islanding function and offline support against any blackout situation. And the support of small-scale distributed generation. Rooftop solar panel systems are the most noteworthy and common example of small-scale distributed generation. The way microgrids are designed must have the most extreme conditions insight and they must provide power both when the grid is available and when it is down, in perpetuity.
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