Why Care About the Duck Curve?

As part of SF Climate Week 2024, former SF Giant Hunter Pence talked on stage with Harvest CEO Jane Melia and Impulse CEO Sam D'Amico about the duck curve and why we need to care about it.  Sponsored in part by Starshot Capital and The Abundance Institute, the Gigaton Salon at SF Climate Week focused on Gigaton-scale solutions to climate change. 

As we electrify our cars, homes, and industry, we need to pay attention to how all those additional electrons affect the reliability and cost of the electric grid. Jane and Sam talk about how batteries help make our daily habits cleaner, more cost-effective, and more comfortable while smashing the no good, very bad duck curve.  

What is the duck curve?

Hunter Pence: Jane, I am very excited to learn about the duck curve and why we should care about it. 

Jane Melia:  During a day in the life of a grid operator, you have a high cost of generating electricity in the morning and the evening, and high emissions. In the middle of the day, lots and lots of lovely, clean, cheap solar.

You’ve got his mismatch and that shape looks like the belly of a duck. We need to use electricity in the night and in the morning. And it actually gets worse as we ask more of the energy grid. For example, two-thirds of the energy used in our homes is for heating and hot water.

That's mostly from burning methane in our furnaces and water heaters. And we have to stop doing that. I mean, we can't beat climate change if we keep using methane in our furnaces. The challenge is: we all need to heat our homes at the same time. You can't say, “Sorry, kids, we're not going to put the heating on til lunchtime!” You have to heat in the morning and at night. That adds load to the grid and makes the duck curve worse. And there are other things - like, when do we cook? We often cook in the evenings. Same thing, same problem. And this is something that Sam can really solve. 

Fifteen years ago, people would have said “We don't have the technologies to beat climate change.” We do. And this particular problem, Sam and my team, we can really fix for everybody.

How does Harvest address the duck curve? 

Hunter: So Jane, why did you start Harvest? Tell us a little bit about your heating and cooling system and how it stores energy.

Jane: What was mind-boggling to me was just two things: home heating and hot water represent 10% of overall climate emissions. Most people don't know that. And Harvest fixes that.

The Harvest system avoids about 55 tons of CO₂ over the life of the system. That's a bigger savings than switching out your old gasoline car and getting an electric vehicle. So the impact is huge, and we do that while saving on bills. We're saving 30% month after month for every home, with a very compelling upfront cost.

And our customers love the system. Nice and warm, all the hot water they need.

What Harvest does is we beat this duck and make home electrification really scalable. We're operating the heat pump in the middle of the day when electricity is clean, cheap and abundant.  And when that heat pump is most efficient. And then we're going to store that in a thermal battery—essentially a hot water tank. 

We store that in the battery and deliver it to your home as heating and hot water whenever you need it. 

It saves you money because it's more efficient and you use electricity at the cheapest rates. It helps the grid get cleaner and it really solves the duck curve. 

We can get methane out of our homes, and we can do it without hurting the grid, and we can do it while giving people an awesome experience while saving money. The question now is getting the word out.

How does Harvest’s battery work?

Hunter:  I want to finish up with more about the battery and how your batteries work, exactly.

Jane: Ah, my favorite question. When we think of batteries, we usually think of the little ones we put in our laptops. We also think of lithium-ion batteries. What we're talking about in our case is thermal batteries. And there's a place for different types of batteries. For thermal loads, a thermal battery is the way to go.

And that's essentially using a sink of heat, in our case hot water, stored up in a tank for later use. We're using the tank as your battery. Why? Because it's cheap. Why? Because it's safe. Because it's durable. It never degrades over time. And it doesn't use any rare earth minerals. So that's how you scale the thermal side of the pie. For your heating, your hot water, and ultimately your cooling. 

Lithium-ion batteries are really what you need for your electric load. Think your stove, think your dishwasher, think your dryer, and so on. They're very complimentary. There's going to be different uses for each. If you're thinking about changing out your heating, put in a battery - but make it a thermal battery.

What else can we do to smash the duck curve? 

‍Hunter: What can people here do to smash their own duck curves?

‍Jane: Switch off gas.  Get heat pumps.  Get storage. That's two-thirds of the energy use of your house. That is a really, really big deal. 

‍Sam D'Amico:  There are multiple ways to roll out energy storage, both thermal and electrochemical. Energy storage is what's needed to do this.

 And it's like it's not just us on stage, but a number of other companies in the Bay area working on this problem. But the big point is, making storage easy to install and ubiquitous is going to solve the duck curve. 

‍Jane: It's all about, first of all, if your gas furnace is about to die or if your gas stove is about to die, please, please, please don't put another gas appliance in. It's going to stay there for a long time. So let's not do that. 

And then it's about getting the word out. You guys all now know we can beat the duck curve. Let other people know because the solutions exist. And it's about now getting the word out about Impulse, about Harvest, about others. Because we can do this. We just need to grow.

Hunter: That deserves the biggest round of applause. Thank you for creating the solutions. That's what Climate Week is about.

This interview was lightly edited for length and clarity. You can watch the entire interview here.

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