Emissions-free energy system saves heat from the summer sun for winter | Hacker News Reader

Emissions-free energy system saves heat from the summer sun for winter

chalmers.se

96 pointssigna1142 comments

These liquid Norbornadiene Photoswitches have an energy storage density of up to .559 MJ/kg.[1]

For comparison: Mechanical Flywheel- 0.36–0.5 Lithium-ion battery- 0.36–0.875 etc...[2]

[1] https://www.nature.com/articles/s41467-018-04230-8 [2] https://en.wikipedia.org/wiki/Energy_density#Energy_densitie...

So, it's as good as a "good" flywheel? or as good as a middle of the road lithium-ion battery? That's interesting!

If so, storing a season's worth of heat might not be so feasible. A home in northern Europe needs about 30,000 MJ, so that would be 53,000 kg of norbornadeine.

If the system absorbs energy during the day and releases energy at night, it might work with quite a bit less (maybe only a few hundred kg). It's interesting that the article doesn't suggest that. I wonder if there is a reason that wouldn't work--not enough solar energy in the winter, perhaps?

Your solar collectors will still be pulling in 1/3 of summer sun in the middle of winter (rough estimate, varies by latitude and weather, void above arctic circle). At the edges of winter you’d even be gaining energy still, so let’s say 40,000kg. That fits in an underground tank typically used by gasoline stations and could be filled by two tank trucks. Sounds doable in the scheme of new house construction, subject to the cost of the chemical of course.

But, I have to think that if space is available, increasing the collector area to gather more winter energy and reducing the inventory of chemical and energy would make more sense.

In the summer you could sell your saturated chemical to industry and have them replace it with unsaturated to offset your panel cost.

Of course now that I have introduced shipping… who wants to live in a shiny reflector farm? Cover industrial buildings and car parks with reflectors, ship or pipe the chemical to houses and have a nicer domestic landscape.

I wonder if there are degradation issues? They make a point of being able to store for 18 years which probably only interests survivalists, but make no mention of cycle limits.

Assuming the at-scale cost is similar to gasoline, it would cost ~$75k just for that much material.

If you assume the useful life is 18 years, you would have to spend >$347/mo on heating/cooling for it to be worth it.

You're suggesting buying pre-charged sun juice? That seems less helpful.

TFA suggested you can have much less by recharging it, and did not suggest the fluid expires ever (suggested otherwise, actually). It holds energy for 18 years, but can be used in cycle forever.

A home in northern Europe needs about 30,000 MJ

Really? We live in central Sweden, just outside Gothenburg. According to the estimate from our power company, our house uses about 15,000 MJ per year - and we have a single floor 200 square meter house. It's rated "C" in energy efficiency (which is the minimum rate allowed for new housing now).

I live in a house from 1909, with a heat pump (bergvärme). We probably use 18000 kWh for hearing in a year, 64800 MJ, at 190 m2 plus basement. 30000 MJ wouldn’t be enough for us I guess.

Do I calculate right that plain water stores energy around 0.2 MJ/kg when heated by 50 degrees celsius? (Specific heat is 4 J/gK) If I am right, ot feels like it would likely be cheaper to just make seasonal heat storages with water.

https://www.ecovat.eu/?lang=en aims for water of 90 degrees Celsius (a 70 degree difference with room temperature), and claims heat can be stored with 95% efficiency (possibly exaggerated; the site also says ‘over 90%’) for more than 6 months in a tank 16m deep and 13m in diameter.

And if it leaks into the groundwater you only have to worry about the anti fouling agents you put into the tank, and anything leaching out of the tank lining.

Are you sure they're talking about the same thing? Norbornadiene has a formula of C7H8, while the OP team's molecule is composed of "carbon, hydrogen and nitrogen". But thanks for posting some context on current research anyway!

IIUC the good part of these molecules is that the energy storage is very stable. With a flywheel the friction will stop it in a few ¿hours/days? The batteries also discharge too fast to store the energy for months. In other comment, someone else proposed to store the energy in hot water, but it's also difficult to keep the hot water for too long.

My first thought was about Drake Landing in Alberta. They use heat pumps and store excess summer heat in the ground for use during the winter[1].

Nifty that this is a new molecule for long-term rather than seasonal storage.

[1] https://www.dlsc.ca/

Does anyone know of similar technology for the inverse? Saving cold from the winter for the summer? With hotter summers and more extreme temperature swings to be expected, it might cut costs on running the AC's

Research thermal mass storage. Basically fill your house with heavy stuff and then insulate the outside walls well.

It works for both winter heating and summer cooling

For thousands of years ice and snow have been gathered in winter and stored for various summer usages in purpose-built structures, ideally underground: https://en.wikipedia.org/wiki/Ice_house_(building)

You can do the same thing today simply by burying tubes in the ground, at least 6 feet down. The ground is cooler in the summer than the air, and warmer in the winter. This can pre-heat and pre-cool air for your HVAC system.

It's been around a long time, I'm surprised almost nobody uses it.

No risk from radon gas?

No, the tubes exchange heat with the soil, not air. If mildew is a problem, you can run coolant instead through the tubes, with a heat exchanger in the building.

There would be an increase in the amount of Radon pulled out of the ground. Usually the way an HVAC system is set up is that you have the filter, then the evaporator coils, then the fan, then the ducts to the rest of the building. To heat or cool the air the tubes would need to be placed before the evaporator coils or it would just be wasting energy instead of saving energy. This also puts it before the fan. Everything before the fan is at a negative relative pressure and everything after it is positively pressurized.

Presumably those tubes aren't perfectly sealed so the negative pressure will draw in a tiny bit of Radon from the ground. You could flip things around and move the fan to right after the filter and before the tubes and evaporator coils, I'm not 100% sure why that isn't normally done but all of the residential HVAC units I'm familiar with are done this way so there's probably a reason.

I can't personally because 8 inches down is solid rock. To remove all that rock would cost a fortune to get down to 6feet.

You and most of the Southwest iirc.

For a ground heat pump system you don’t need to remove the rock. You just drill a hole into it. My parents did this and their house is built on top of solid rock.

Do you use it?

No and I strongly regret not doing it when the house was built. It could have been done then at minimal cost.

https://en.wikipedia.org/wiki/Heat_pump

Do you mean that?

https://en.wikipedia.org/wiki/Geothermal_heat_pump

In the north the frost line can get to below seven feet, and even past that you're now pulling cold air in, instead of recirculating already heated air from the house. I think this would work well in trying to cool a warm house, or warm one that experiences very mild cold, but I imagine it has limited application.

All HVAC systems must pull fresh air in from outside. Even if the ground is colder than the house, it is warmer than the air outside and so is useful to pre-heat the air.

For example, if it's -10F outside, and the tubes are below the frost line, that can warm it up to 32F before needing an active heater to boost it the rest of the way.

Modern furnaces only pull air in from outside to burn, run through the heat exchangers, then it's blown back out - the air that's moved around inside the house is simply recirculated. Where would the air from the pilings be pulled? We would need a huge reservoir of air to prevent carbon monoxide combustion issues.

I don't think that's correct (and it's certainly not correct for my system). Not drawing in outside air from time to time will make the indoor air quality very poor.

Is your furnace high efficiency? Older models take in air from the house and then blow it out the chimney, but it's different in newer systems. The intake/exhaust are both pressurized and at least exit outside the house (in most setups they pull and exit outside, but I have seen where the intake is inside). The cold air return is usually in the basement and then just blows hot around your house. And yes, the air does get stale in winter.

Modern furnaces take in outside air for combustion. Using up inside, warm air for combustion is doubly inefficient since you expel exhaust air you already sunk energy into and you are sucking cold air that has to be heated from a much lower temperature.

Modern code for cold climate houses is to be air sealed. A heat exchanger draws in fresh air, raises the temperature with existing heat and then expels cold, stale air outside. Very efficient.

When air sealing was new many buildings developed longevity issues like mold since any moisture issues couldn't dry. All those problems have been worked out and there are homes in extreme cold climates that don't need any energy from the grid they are so efficient.

https://en.m.wikipedia.org/wiki/Norbornadiene

Wikipedia has a pretty thorough chemical description. Fascinating, really.

A long term storage system has to have very low capital cost, as it doesn't have many cycles over which to amortize that cost. I doubt this system makes any economic sense.

Trying to figure out marginal cost. I think some part of it uses coal tar as a precursor. It might actually be pretty cheap and/or the US may have a comparative advantage given how much coal it has.

The revolution isn't as long term storage, it's as a closed cycle, carbon neutral, solar-powered energy capacitor with relatively high capacity per kg.

Long term storage is just nice to have.

I'm the process of building a "breadbox" + coldframe hybrid to warm hot water using the sun.

Similar design:

https://youtu.be/tqUwBwfN5iE

> He hopes that the research group will shortly achieve a temperature increase of at least 110°Celsius ..

So, enough to boil water? Once you can execute a phase change you can generate electricity, not just heat....

Can this also store heat from electricity?

If so I’m wondering if this couldnrevolutionitize the lowly water heater.

I believe they use a lot of energy just keeping their tanks at the right temp.

It's weird that the article has no data about the molecule. You can find it in the research articles "linked" at the bottom.

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