By Michelle Peters. Michelle is an Associate Program Manager at Energy Sciences. The firm helps clients meet energy challenges with practical solutions that reduce waste and increase net operating income.
I was recently asked what I would call my TED Talk, it did not take long for me to respond, “Demand Response: It’s not just for energy nerds”. TED hasn’t invited me to speak quite yet, but my goal for this blog is to bring you a topic that I am passionate about in a more approachable way. We all expect that when we flip a switch, turn on the TV, or push a button to make our morning coffee, it will happen. We rarely think about how this is delivered to us, or how events like extreme weather patterns effect it.
First, Some Background Information
A good place to start is defining demand; demand is the overall amount of electricity that is being used at any given time. Keep in mind that in general electricity needs to be generated as it is being used, so infrastructure meeting demand loads is a critical piece of delivery to you.
Next, we need to explore peak load and peak demand. Peak load is the total amount of electricity that can be generated by an electric power substation. Power plants and their substations are designed for the greatest possible anticipated peak load. On average they may reach this load between 10-20 times per year. Peak demand refers to the total amount of electricity that is needed to power the group of customers who receive electricity from a substation. When demand is greater than the output, we run into issues like unexpected power loss. Typically, this happens when we will be expecting our electricity to be stable the most, extremely hot weekdays in the summer.
When temperatures rise, electric use also rises because of the added use of systems like air conditioning in addition to the normal load. Demand Response is simply analyzing that usage and deploying a strategy to shift some of it to a lower usage time of day, avoiding reaching or exceeding peak demand. This minimizes the chances of unexpected power loss, brown outs, and damage to infrastructure like substations and transformers. This approach has been used successfully with commercial and industrial customers, who receive notification of a peak demand day approaching allowing them to shift their production line shifts to evening or overnight hours, this can also be built into their rate structure.
Some residential Demand Response programs have used air conditioning cycling to help curb usage during peak demand days. This is done by installing a device on the AC condenser which will cycle periodically during the event. While this strategy works, it can lead to customers experiencing varying levels of discomfort, especially if the cycling time of the AC cannot keep up with temperature rise. Another approach, which is growing, is the use of smart Wi-Fi thermostats (like Nest or EcoBee) combined with AMI (commonly referred to as “smart meters”). The data from usage from AMI along with the smart thermostat can be used to accomplish the following: send push notification to customers through their mobile phone of upcoming peak demand events, understand factors like your homes age and size, and engage a precooling schedule for your home before the peak demand event. Pre-cooling is the act of running the AC before the event to set your home to lower than normal temperature so that it will gradually rise during the event. Pairing the pre-cooling with the use of ceiling fans on a low level will also help with maintaining your overall comfort during the event.
How Precooling Works
- The outdoor temperature is expected to reach 95ﹾF
- A Demand Response event is called from 1PM – 6PM, that is 5 hours during the hottest part of the day
- Temperature rise can be expected indoors to occur at a rate of 1-3ﹾF per hour
- This can be affected by factors like the age of home, if it is well insulated, and the estimated age of the HVAC system
- If the house is precooled to 71F, we can expect a gradual temperature rise by the end of the event to between 77-80F.
What can you do to help reduce peak demand?
- Check with your local utilities to see if they have incentives which either offset the cost of a smart thermostat or provide one free of charge.
- Shift high usage activities like running the dish washer, washing your clothes, or charging electric vehicles to the evening, overnight, or weekend hours.
- Opt-in, some utilities allow you to “Bring Your Own Device” and participate in Demand Response events; this would be an option if you already have a smart thermostat.
The Bottom Line
Upgrading infrastructure is costly, and in addition to the periodic outages you would experience during an electric substation upgrade, it’s incredibly wasteful. We build our electric infrastructure around peak demand events that may occur 10-20 times a year, to me that is the equivalent of buying food to prepare for a holiday meal every time you go grocery shopping—resulting in a large amount waste. Some utilities are using strategies like demand response to help reduce waste, and even reduce the overall electric load.