We are physicists and professional tinkerers:
Tinkering means for us: To ferret out how something works in detail - and to use these insights to build creative solutions, ideally from existing components! As MacGyver did!
punktwissen means: Technical information and vendor-agnostic consulting boiled down to the essentials. We want you to know and understand your systems in order to make independent and informed decisions.
Most textbooks introduce Carnot's cycle for an ideal gas – but the efficiency would not change if the substance had a different equation of state. Motivated by a paper about Carnot's efficiency for a machine using Van der Waals gas, I calculated the efficiency for a more general class of substances.
Comparing measurements of the volume of ice in the tank with simulations - based on a model of the control logic, the varying performance factor of the heat pump, heat transport in ground, energy balances for the hot and cold tanks, heat transfer via heat exchangers connected in series.
From the theory department: Why can’t there be any heat pump / heat engine better than Carnot’s reversible machine? A closer look at the proof by contradiction.
Solution of the Heat Equation, based on the simple assumption of a harmonically varying surface temperature, plus a superimposed geothermal gradient. The results can be used for cross-checking the value of the thermal diffusivity of ground.
At the beginning of February we had turned off the solar collector to mimic a harsher winter. The ice cube, generated by our heat pump since then, stopped growing at about 15m3. About 10m3 of water remained unfrozen. Toying with theories about heat transport ...
punktwissen - Professional Tinkerers
Heat Conduction Cheat Sheet (2018-09-24)
Temperature waves – simulating yearly and daily oscillations in the temperature below the surface of the earth or near wall/floor of our ice/water tank. Stationary solutions – to assess the heat transport between pipes and the medium they are immersed in, like the tubes making up the heat exchanger in the tank or the solar/air collector.
Can the Efficiency Be Greater Than One? (2018-04-09)
What is efficiency actually? The ratio of an output and an input energy – however these may be defined arbitrarily, and input and output are determined also by economics, not only by physics. So the answer is actially: Yes! I provide a non-exhaustive collection of examples.
The Heat Source Paradox (2018-01-19)
"A simple relation between a heat pump system’s key data; yet used in a misleading way in adverts: The worse the performance is, the smaller the heat source can be built."
Simulating Life-Forms (2): Cooling Energy (2017-11-28)
I found an incredibly detailed research report by the Australian government – about energy use in private homes, by appliance and purpose. It confirms my reluctance to 'predict' cooling energy as usage of air conditioning depends strongly on life-style choices.
Back to basics – how do the famous physicists introduce entropy and statistical mechanics in general?
The Collector Size Paradox (2017-11-01)
‘Collector harvest’ does not change much if we only use half the collector. Perhaps counter-intuitive but explained by the characteristics of heat exchangers connected in series: Especially if one of the heat exchangers (in the tank or collector) is already much superior to the other one, it does not help to optimize the good one further.
Tinkering, Science, and (Not) Sharing It (2017-09-17)
That moment when you realize that your tinkering with PVC piping is actually science. Getting nostalgic about my nerdy childhood hobbies.
Simulations: Levels of Consciousness (2017-08-17)
Getting philosophical – what is a simulation (of our heat pump system), and what are the challenges? For modern buildings, simulating 'user behaviour' can be as critical as simulating 'physics' and control logic.
You Never Know (2017-05-25)
… when obscure knowledge comes in handy!
Mr. Bubble Was Confused. A Cliffhanger. (2017-04-08)
Our automated level sensor underestimated the volume of ice in the melting phase. In the coldest January since 30 years Mr. Bubble ware driven over the edge. He had to deal with a cliff … of ice.
Ice Storage Hierarchy of Needs (2017-02-22)
Mulling upon ‘Peak Ice’ in our heat pump system – and detailed simulations versus simple energy accounting. Why the maximum volume of ice obtained in a season depends sensitively on the properties of ground and the collector.
A physicist’s musings about the unit used to characterize solar panels’ peak power: kWp.
An invention – an answer to: Can a compression heat pump be built in a completely different way? Yes, the pressure gradient can be created by centrifugal forces!
Alien Energy (2016-04-15)
Our photovoltaic generator is up and running for nearly a year. In this post I analyze the most remarkable day – as per our data logging, when we got nearly the generator’s rated power in mid-winter. Re-visiting the impact of temperature on output power, and the 'focusing' / 'edge of clouds' effect.
Re-visting heat transport and heat diffusion length, this time only analyzing dimensional relationships. I introduce the concept of dimensional analysis by answering the question: How does the speed of a rowing boat depend in the number of rowers?
You need to get a feeling for numbers 'in renewable energy' - and it more than baffles me when authors of click-bait articles don't bother to the most basic cross-checks. It seems we lost the feel for 'what can power what' when engines replaces horses and humans.
An account of the 19th century invention, based on the original German research reports.
Heat Pump System Data: Three Seasons 2012 - 2015 (2015-09-29)
Brief summary of last season's performance, plus back-of-the-envelope estimate of economics: Heat pump versus natural gas, based on costs of energy in Austria.
Finally two science geeks did a careful experiment - proving that vortices on either hemisphere rotate in different directions. I just like to point to a pioneer who did such an experiment long before the social media era - in 1908.
An Efficiency Greater Than 1? (2015-06-01)
The Coefficient of Performance of a heat pump is much greater than 1 which is due to the definition, omitting input 'ambient energy'. The rather high factor gives proof of the fact that heat pumps operate well above absolute zero.
How to Evaluate a Heat Pump's Performance? (2015-04-21)
Definitions of performance indicators and how to determine them – comparing alternative methods, based on sensors available (Coefficient of Performance / Seasonal Performance Factor). Bonus: Cute math puzzle as the comparison boils down to: When is the ratio of averages equal to the average of ratios.
Solar power and the impact of a solar eclipse. Soon we will contribute - our PV generator has already been ordered.
A Sublime Transition (2015-02-14)
Phase transitions between water, vapor, and ice: Last winter’s viral trend of freezing boiling water in mid-air, and discovering that scientists discuss such effects to this day.
A simplified simulation based on historical weather data: How large should this tank be so that it would hardly ever freeze completely in typical Eastern Austrian winters?
Being Creative with What Is Available (2014-11-27)
Build something from anything and to use whatever tool is at hand! Refers to anything we ever did or built - in the physics lab, as software developers, on designing the heat pump system.
All Kinds of Turbines (2014-10-16)
Again some back-of-the-envelope cross-checks, this time related to hydro power.
Pumped Heat from the Tunnel (2014-10-04)
Summary of a press release that announced a EU 'Smart City' project. Cross-check of numbers for a large heat pump system. The heat source is water from a tunnel.
On the arcane nature of pipework, path integrals, and public key infrastructure.
Grim Reaper Does a Back-of-the-Envelope Calculation (2014-06-22)
Some crude estimates related to the physics of scything - and why it might be so exhausting.
Greatest Innovation Ever (2013-09-04)
Thoughts on the power grid - tangentially related to heat pumps that are often considered sort of buffer that will help to stabilize the smart grid (via demand side management).
The Falling Slinky and Einstein's Elevator (2013-04-03)
It's fascinating that it is not easy to explain seemingly mundane classical mechanics!
On Coriolis force.
Intuition and the Magic of the Gyroscope - Reloaded (2013-03-13)
Reloaded: It seems that gyroscope is one of the most searched for terms on this blog. I dish what you long for, readers!
The First Heat Pump Ever Was Built in Austria (2012-12-10)
History on engineering - set in my home country.
Microwave Ovens Are Not Rodent-Ready (2012-11-16)
One of the top posts on this blogs. I am happy to help out fellow netizens with their issues with mice in microwaves.
Einstein and His Patents (2012-11-02)
... his refrigerator patent in particular.
I missed the most amazing light bulb's birthday - the least thing I could do was to write a post.
The Spinning Gyroscope and Intuition in Physics (2012-09-05)
Do we understand the gyroscope really? Marveling at Feynman's explanation and new(!) papers on explaining it.
Why Do Heat Pumps Pump Energy so Easily? (2012-05-10)
Brief (yes, really) explanation how a heat pump works.