Google-born startup thinks it’s time for a ground-source heat pump renaissance

Seeking to do for home heating systems what SolarCity did for solar panels, a new company called Dandelion hopes to popularize decades-old, energy-efficient heating and cooling technology.

So-called “ground-source heat pumps” or “geothermal heat pumps” have been used for decades to warm and cool homes, especially in colder climates where expensive fuel oil is burned for warmth. The pumps use the relatively stable temperature of the Earth below the frost line to pull up and push down heat using pipes filled with a water/antifreeze solution (or food-grade propylene glycol, in Dandelion's case). Although ground-source heat is an old and proven technology, Dandelion says it has made a few advances to the installation process and business model that will make these systems a more attractive proposition for homeowners.

This is important because heating is still a sector of the global economy that relies heavily on burning fossil fuels, and cooling has a similar problem—running an air conditioning unit is really energy-intensive. In the summer, ACs represent considerable load that utilities have to plan for, usually with fossil fuel-burning plants. (Ground-source heat pumps require electricity, too, but we’ll get to that below.)

How does a ground-source heat pump work?

At relatively shallow depths in the Northern Hemisphere, soil tends to maintain temperatures equivalent to the mean annual air temperature above it (between 50 degrees Fahrenheit and 60 degrees Fahrenheit, according to the Department of Energy) year-round. Seasonal temperature variations are limited. So ground-source heat pump installers place solution-filled pipes underground either horizontally or vertically.

With the help of a heat pump, the solution that circulates in the pipes transfers heat from the ground to the building in the winter. During the summer, the solution forces heat out of the building and underground. According to a 2007 paper (PDF) in Environmental Research Letters, ground-source heat pumps can “provide heating using 25 to 30 percent of the energy consumed by even the most efficient conventional alternatives.”

There are drawbacks, of course. Installing the right ground-source heat pump technology is important—the details of the installation depend on the location of the home, property size, soil composition, and other conditions. Since heat pumps need some amount of electricity to operate, their greenhouse gas-avoiding properties depend on how much renewable energy your local utility uses, too. And the Environmental Research Letters paper points out that there are concerns that the energy used to power some ground-source heat pumps could have higher system-wide emissions than keeping a newer, high-efficiency furnace. So not every household needs one of these immediately.

Where does Dandelion fit in?

Dandelion claims that it has simplified the variables that go into a household’s decision to get a heat pump. The company grew out of Alphabet’s moonshot lab, formerly Google X, which has poured money into research that advanced projects like self-driving cars (Waymo), head-mounted mobile computers (Google Glass), and healthcare diagnostics (Verily).

Ars spoke to Dandelion’s CTO, James Quazi, about the project. Quazi said that Dandelion is only installing two-stage heat pumps right now—a relatively old technology compared to variable-frequency heat pumps that can modulate the heating and cooling work done by the pump’s compressor. But eschewing more cutting-edge technology for a pared-down technology that Quazi called “battle-tested” could help Dandelion keep costs down. After all, being able to show that ground-source heating offers economic savings is a priority for the company.

Specifically, Dandelion’s system uses a heat pump with a heat exchanger attached to one or two 400ft pipes that are buried vertically (yes, vertically) in one or two four-inch-wide boreholes drilled into your lawn. (“500 [feet] is generally the max you’d want to go, and further requires mining permits,” Quazi said.)

The pipes are filled with a mixture of water and propylene glycol, which captures the relative warmth of the surrounding earth. That mixture is then pumped up to a heat exchanger, where it lends that low-grade heat to a refrigerant, which is sent through a compressor to bring the heat up to 134 degrees Fahrenheit—a temperature that could actually warm a house.

One thing that’s new is how Dandelion drills those boreholes. “Generally, well-drillers use existing equipment,” Quazi told Ars, often using mining drills that produce six-inch holes in the ground. The installers then insert two, 1.25-inch pipes, connected at the bottom by a U-shaped pipe. But you don’t need a six-inch hole for little more than 2.5-inches of piping. Instead, Dandelion is retooling the traditional machinery to only drill a four-inch hole, which it claims reduces the amount of debris that needs to be hauled away and makes the drilling process more economical.

Additionally, the company said it has purchased some custom drilling machinery that will come complete with modifications specific to drilling in upstate New York, where Dandelion will be offering its first installs. In that area, before you hit rock, you’ll encounter some amount of what Quazi calls “unconsolidated soil.” In a traditional ground-source heat pump installation, that soil needs to be reinforced by steel tubing called casing.

Installing the casing makes vertical ground-source heat pumps vary widely in price, because drillers are never sure how much each project will need until the project is underway. This causes problems for customers who want a simple installation quote. Instead, Quazi said, Dandelion will use resonance sonic drill heads to liquify the earth in the drill path. This will allow the company to install up to 60 feet of casing “in about 10 minutes.”

A local endeavor

Quazi said many of his team members got started working for SolarCity, so they’re trying to adopt a business model similar to the one that helped that company become one of the leading residential solar installers in the US. That is: target a market where the economic and environmental savings are obvious, and scale out from there.

For ground-source heat pumps, that market is upstate New York. There, you’ll sometimes find extreme weather, and many houses depend on expensive fuel oil or propane for heating. Dandelion will be targeting homes of a certain size (“mega-mansions are not our target market,” Quazi said), and the company will give preference to homes that are heated and cooled with forced air, which is compatible with its system.

Additionally, New York has an abundance of greenhouse gas-free nuclear energy and renewable hydroelectric generators serving its grids. Using electricity to power a ground-source heat pump isn’t necessarily giving up fossil fuels locally just to export those emissions to the power station (although natural gas-fired generators do still play a big role in New York).

Quazi was frank about the fact that a Dandelion system isn’t going to offer savings for all homes—he said if you heat your house with natural gas, the system isn’t going to pay for itself due to natural gas being so cheap.

But if you do qualify, Quazi says Dandelion has standardized the installation so a system costs about $20,000 cash, or the company can offer a payment plan to make the install about $150 a month.

As with everything these days, the system also comes with a software end. Sensors are installed throughout the system so that the company can figure out when and where maintenance needs to be done. Analytics will also show the customer how much money they’re saving, and Quazi said that, by gathering data, Dandelion will be able to do predictive fault detection, so it can predict a component will fail before it actually does.

For now, the company is working on building a small backlog of a few dozen qualified customers who would see the most benefit from such a system. Then, Quazi told Ars, installations should begin around late September. After those installations, the company plans to take a break in late 2017/early 2018 to regroup and focus again on sales and marketing before proceeding with new installations later in the year.

If that doesn’t work for you, more traditional geothermal companies have been quietly expanding in the last several years, as well. According to a report compiled by Navigant Research for the business association Advanced Energy Economy, revenue from the sales and installation of geothermal heat pumps in the US has grown steadily in the past six years, “rising from $93.6 million in 2011 to $154.3 million in 2016, with an increase of six percent from 2015 ($145.1 million) to 2016.” Dandelion hopes that those increases grow even more in 2017.

Listing image by Dandelion