Despite my attempts to post mainly geeky and weird stuff peppered with (very often not down-to-earth) physics, I got involved in some serious discussions on renewable energy, sustainability, heat pumps, and the pleasures of Building Your Own Stuff. So I will describe what I am actually working on / playing with when I am not blogging, liking, sharing or tweeting.
Elkement is an amalgam of my first name, Elke, and one of my nicknames, The Subversive Element. I have a penchant for the words elementary and elemental, any puns comprising those, and I like geek gadgets exhibiting the periodic system of elements. It is straight-forward that I have to work on a heating system that utilizes The Four Elements: Earth, Wind, Air and Fire.
As usual, I first considered this an incredibly creative way to describe a heating system – until I discovered that zillions of companies in the HVAC business use the same analogy. Besides I like the philosophical, if not new age-y, connotation contrasting with down-to-earth engineering.
I (we) work on optimizing a heat pump system that uses these said elements, which actually is: An unconventional source of heat that makes the system different from geothermal, ground water or air source heat pumps.
This is a simplified schema. Please bear with me!
The Four Elements are indicated: A rather large (about 20 m3) tank filled with Water is heated using an unglazed solar collector.
This collector allows for harvesting energy from solar radiation (Fire), but – above all – from ambient Air via convection.
The tank is located below ground (Earth). Actually, in the prototype system the ‘tank’ is a former small cellar that once had been used to store potatoes and wine (This is common in the region where I live). The cellar had been lined with plastic sheets which makes it a pretty cheap tank. There is an average net flow of energy from the ground to the tank – it would be detrimental to insulate the bottom and the side walls of the tank.
The water tank constitutes the heat source: Instead of burying pipes in the garden (ground source loops), the heat exchanger pipes are immersed in the tank.
It is a single (simple) closed cycle:
Heat pump –> solar collector –> tank –> heat pump
The combination of the tank and the collector is the actual heat source of the heat pump.
Depending on the temperature difference between ambient air and the tank and on the heating demand of the building the controller decides whether the collector is used or circumvented and whether the heat pump is turned on.
The heat pump heats two different hot water tanks – one is for heating the tap water, the other one is for transferring heat to the room heating loops. A heat pump cannot be “dimmed” continuously to different output powers: It delivers heat at full power or it is off. Thus you need an intermediate storage that allows for gradual heat transfer to the heating loops.
There is an important 5th element (You have expected me to add a link like that, didn’t you?): Ice.
During the heating season about 75% of the heating energy is harvested from air and fire channeled through the solar collector, freezing of the water in the tank and heat transfer from the ground yields the remaining 25%.
But heat pumps are cool, and this setup allows for a simple way of passive (“free”) cooling: In summer the room heater becomes a cooler: The ‘Hot Water Tank for Room Heating’ becomes the heat exchanger that transfers heat from the room heating loops to the underground tank. The heat pump can still heat the tap water in parallel – actually this is beneficial for cooling!
The overall goals for this design have been:
- Using a heat pump with a high seasonal performance factor, but avoiding the drilling of deep bore holes or having to turn the whole area of your garden into a huge pile of soil temporarily.
- Using rather simple, state-of-the-art components that could be purchased by home owners in online shops and that would allow skilled Do-It-Yourself enthusiasts to built the system themselves.
- Allowing for cooling without adding complicated components or needing air-condition (to American readers: AC in homes in uncommon in Europe).
Further reading: This was the pre-quel of the story (“How I started loving heat pumps more than IT.”)
Our German blog has more detailed technical information – I am not sure of we will ever provide the same level of details in English.