2022-12-12 7 min read


Notes, 2022-12-12.

I love the holes dogs dig in the shape of their bodies to make little sunken nests to stay cool in the summer. While the top layer of the ground might bake in the sun or freeze in winter, you only need to scuff the surface to find more moderate temperatures. Seasonal temperature swings percolate slowly through the soil, so a meter down, the earth in winter still holds some heat from the summer before. A few meters below that, the temperature of the Earth’s crust is constant year round, roughly matching the average annual air temperature – meaning the ground is warmer than the air in winter and cooler in summer. Our species has known about and sought comfort in this thermal stability for ages. Ancestral Puebloan cliff dwellings etched into canyon shelves, semi-subterranean barabaras, and hot spring baths are all methods for reaping the benefits of the heat of the Earth’s formation, the radioactive decay of elements in its molten core, and the slow pace at which heat travels underground.

As a kid, probably after reading some book about homesteading, I lowered a zipped bag of grapes into the creek behind our house, hoping to come back later to find them naturally refrigerated. It didn’t work; by itself, a creek can only cool a bag of grapes to the same temperature as the water they’re submerged in, just as a root cellar only keeps things as cold as the ground. But we now have ways our ancestors didn’t to pump heat directly from one place to another, amplifying our age-old relationship with the earth. Heat pumps work by using a small amount of e to force a refrigerant through a cycle of compression, condensation, and expansion, much the same way a refrigerator works. Some heat pumps transfer heat to or from the ambient air, some from water, and some from the ground. If I’d had a heat pump, I could have used the stream as a heat sink to freeze the grapes solid – and more.

-Natasha Balwit-Cheung

The most clicked link from last week's issue (~6% of opens) was a story about “THAT COMPANY WHOSE NAME USED TO CONTAIN HTML SCRIPT TAGS LTD”.

In Slack, Members have been exploring ChatGPT's capacity to solve engineering problems, with mixed results. Many of the outputs have errors, sometimes glaring and sometimes subtle. But with iteration and debugging there are interesting results. This demo shows it outputting well-commented structured text for a PLC – wild!

Planning & Strategy.

  • Global sales of heat pumps grew by almost 15% in 2021. The European Union saw the highest growth, around 35%. Of the 2.17 million heat pumps sold in Europe, 94% use air as their energy source, and only 6% use the ground or water. All I want for Christmas is greater market penetration of ground-source heat pumps! They have many advantages over air-source heat pumps: their efficiency dips less in winter, and by using the thermal mass of the ground as a bank to transfer heat into or out of, they add storage and stabilization to the grid. But there are also understandable barriers to adoption, including the high upfront cost of installation, the difficulty of drilling, and wariness from homeowners and installers about the relative inaccessibility of underground components.
  • Lisa Heschong’s Thermal Delight in Architecture elevates the thermal experience (and the design choices shaping it) as an aspect of architecture. It’s an eclectic and emotional history of thermal design in buildings, inglenooks, oases, and all. “Environmental control systems tend to be treated rather like the Cinderella of architecture,” Heschong wrote, “relegated to a backroom to do the drudgery that maintains the elegant lifestyle of the other sisters (such as light, form, structure, etc.).” Yet historically, the parts of a house that served to moderate the temperature of the building – the hearth, the courtyard garden – were beloved gathering spaces. While I wouldn’t want to be trapped in most boiler rooms, I’m grateful that environmental control systems provide an alternative to what Heschong cites as “the simplest way to cope with an adverse climate,” which for many organisms is simply “not to be there” – to stop metabolizing, like yeast in a refrigerator, or scatter seeds and turn to compost like annual vegetation. For humans, in the absence of effective heating and cooling infrastructure and the increasing presence of untenable climatic extremes, not being there means migration.

Making & Manufacturing.

  • Legend has it the first electric ground-source heat pump was invented by an American named Robert C. Webber in 1948 as he tinkered with a deep freezer in his cellar. When scalding water spilled from the outlet lines of the freezer, he thought to use the refrigeration cycle for heat as well as cooling, and so channeled the excess hot water to his boiler. He still had an excess, so he fed the remaining hot water into “a coiled copper tube with a small electric fan,” and heated his whole house. When this worked, supposedly, he built a full size system, circulating freon gas through copper pipes embedded in the ground to collect its heat. Other configurations of heat pumps were described and built before and around the time of Webber’s experiment, so perhaps the story here is not the genius of a single inventor, but the goodness and promise of tinkering.
  • Smocking is a fabric manipulation technique that involves gathering and stitching together the cloth in regular folds or pinches to create a flexible 3-dimensional surface. It adds stretch to fabrics that don’t stretch, and because it creates small pockets of air between the garment and the wearer’s skin, it is insulative in cold weather and allows for comfortable airflow in warmth or physical activity. Originally popular for agricultural workwear, smocking granted freedom of movement and rich decorative opportunity in a loose, sturdy garment. English farm workers wore smocked blouses (eventually just called smocks) sewn from a complete rectangle of cut fabric to minimize textile waste and eliminate the need for a pattern. Clothing and textile production is a significant contributor to climate change, and the energy used to wash clothes is a surprisingly large portion of wardrobe-related emissions. Taking a cue from medieval peasant farmers and pulling on a smock before dirty work is a good habit.

Maintenance, Repair & Operations.

  • Nesta, an innovation-minded charity in the UK, asked gas boiler engineers about barriers to retraining in heat pump installation. Three themes emerged: uncertainty, complexity, and invisibility of demand. Gas engineers were uncertain about how heat pump technology might evolve in the future; whether heat pumps were really going to replace gas boilers, or whether something else like hydrogen might step in; and uncertain about how to pursue certification and adapt their business models. They foresaw complexity in both system installation and the administrative work required to leverage grants and rebates. And they didn’t see demand first-hand – although they recognized this might just be because customers seeking heat pumps would be more likely to ask someone already advertising as a heat pump specialist. Nesta plans to use these insights to design a retraining strategy in 2023.
  • The French town of Chaudes-Aigues built the earliest recorded district heating network in the 14th century, with wooden pipes distributing water from thermal springs. Property records show that access to the geothermal heat network for domestic hot water and heating was widespread by 1474. Over the ages, the waters of Chaudes-Aigues have been used by locals for cooking, bathing, scouring wool, and incubating eggs. Thanks to centuries of upgrades and maintenance, the network still heats homes today.

Distribution & Logistics.

  • In the coming decades, governing bodies will have to confront the distance between their emissions reduction targets and the physical realities of energy transition: the raw materials, skills, supply chains, and implementation strategies necessary to achieve the targets they have set. The UK 2021 Heat and Buildings Strategy has a target of deploying upwards of 600,000 heat pumps per year by 2028, and potentially ramping up capacity to replace ~1.7 million gas boilers each year within the decade after that. Biden authorized the Defense Production Act to ramp up heat pump production in the US, and the Inflation Reduction Act included nearly $9 billion for state and Tribe-administered home efficiency programs.

    Making good use of the funds and momentum means strengthening the whole supply chain, and ultimately bolstering demand as well as supply by providing incentives and financing mechanisms to encourage heat pump adoption and weatherization. The Defense Production Act is a great initial step to boost production. I’m optimistic that organizations like BlocPower, which is taking on workforce training with an eye toward racial justice, and Dandelion Energy, which offers streamlined system design and a financing package, are just early examples of innovative efforts to lead the charge for building electrification and the decarbonization of heating and cooling.
  • A century and a half since the London tube ran the first underground trains, they have generated so much heat (mostly from friction braking) that the ambient temperature of the surrounding London Clay has increased from 14° C in 1900 to 20°-25° C in 2017.

Inspection, Testing & Analysis.

  • While no combustion-based or traditional electric heater is capable of operating at over 100% efficiency, ground-source heat pumps operate in most circumstances with a coefficient of performance (COP) between 3 and 5, or between 300% and 500% efficiency. Their power consumption is highly variable, so high-quality open data on heat demand and performance is a priority for understanding their impact at scale. Older heat pumps suffered from a significant dip in effectiveness in cold seasons and climates, but newer generations can operate effectively at temperatures well below freezing, and the technology keeps getting better. Some testing standards neglect performance analysis in sub-zero conditions, leading to a knowledge gap in the true capability of newer heat pumps in very cold places. But the fact that uptake is highest in Europe’s northernmost countries tells us that heat pumps are still a strategic choice in wintery climes.
  • Spatial alliesthesia is the pleasure of experiencing localized thermal stimuli. Think of holding your head over a steaming mug of tea in a cold room, leaning against a shaded wall in summer, or the bliss of radiant floor heating. While thermal comfort standards for buildings hold a neutral, static, homogenous climate as the ideal, people tend to enjoy temperature differentials. For example, Swedish farmers like their heads to be 4° to 6° C cooler than their feet in summer, and 3° to 4° C cooler in winter, while driving their tractors.


What’s it like to go from working at an organic produce cooperative to an upscale fish factory run by an enthusiastic Brexiteer? Fishy politics, gaming of geographical origin certifications, and workplace (dys)function are narrated with humor from the home delivery subdivision of a Hackney salmon smokehouse.

The Ger Plug-in prototype adds an “infrastructural spine” to the traditional Mongolian ger.

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