Recycling Excess Heat From the Data Center

itwbennett writes "A new data center being built in Helsinki, scheduled to go live at the end of January, will generate energy and deliver hot water for the city. The data center is located in an old bomb shelter and is connected to the Helsinki public energy company's district heating system, which works by pumping boiling water through a system of pipes to households in Helsinki. The recycled heat from the data center could add about 1 percent to the total energy generated by the energy company's system in the summer." The article doesn't say what the overall efficiency of the heat recovery is. Researchers at MIT are working on a new energy-conversion technology based on quantum dots that they say has already demonstrated 40% of the Carnot efficiency limit — 4 times what is achieved by current commercial thermoelectric devices. The researchers believe they can reach 90% of the Carnot limit.

Comments

WTF, why is a Carnot reference here?

[ElSupreme]

How is the Carnot cycle apply here? This is direct heat conversion, and the efficiency should be near 100%, you would have line losses.

Re:WTF, why is a Carnot reference here?

[vlm]

How is the Carnot cycle apply here? This is direct heat conversion, and the efficiency should be near 100%, you would have line losses.

Reading thru a filter of journalist ignorance, I think the journalist is trying to say they're using a heat pump to reject the heat from the cooling system into the heating system's boiling water. There is a Carnot cycle limit to heat pumps.

Re:WTF, why is a Carnot reference here?

[jank1887]

because the summary is talking about two entirely separate topics. (1) Helsinki data center will deliver waste heat in useful form to the city. (2)Researchers at MIT are working on a solid state heat-to-electric conversion element called a thermoelectric device. current devices are at best ~10% of Carnot (practical devices approach 10% total efficiency on a good day), and they say they'll hit 40-90% of carnot with their new quantum dot TEG's. We'll see.

You are correct, though. Carnot efficiency discussion only really applies to (2) not (1). Mister itwbennett just decided to lump these two things into one submission.

Re:WTF, why is a Carnot reference here?

[Snufu]

The summary writer may also have wanted to suggest that thermoelectric devices may be used to convert the waste heat at the data center into useful energy. However, thermoelectric devices are not really feasible for this application. To achieve the efficiencies cited for thermoelectric technologies, you need temperature gradients in the 100's degrees C, as in, for example, a car engine. Typical temperature gradients at data centers are on the order of tens of degrees C. This is considered "low-grade" heat in the renewable energy vernacular.

Re:WTF, why is a Carnot reference here?

[MillionthMonkey]

We've both made errors. I made a reference to "Swedes" and not Finns because I read too fast. However, you said:

Carnot cycles are for calculating heat engines. This is not a heat engine. There is NO WORK being done.

First of all theoretical efficiency limits apply to both types of reversible heat engines- steam engines which extract work and heat pumps (e.g. air conditioners) which require it. (In the heat pump case I guess Th would still be a temperature in the datacenter somewhere, but Tc would now be their hot water heaters' temperatures, not the temperature outside- another mistake I made. These Finns are confusing.) But RTFA- this looks like a heat engine:

Helsinki public energy company Helsingin Energia will recycle heat from a new data center to help generate energy and deliver hot water for the Finnish capital city, it said on Monday.
The recycled heat from the data center, being built by IT and telecom services company Academica, could add about 1 percent to the total energy generated by Helsingin Energia's system in the summer, according to Juha Sipilä, project manager at Helsingin Energia.

You DO have more to stand on here if the water were flowing (say) into some hot water heater before being heated to a desired temperature, so the heater would has less work to do- but what's this then in your post about "transmission lines"? It's clear that work is being done here if they're generating electricity in the summer.

I put electricity into a chip. The chip uses X amount of energy and ~100% of the (electrical) energy is converted to heat energy.

Yes that's conservation of energy. But notice that the energy has been converted into a less useful form, even if the flow goes directly off that chip into someone's bathwater. There isn't enough water being heated by that chip, or if there is, it's too cold for anyone to notice. Finns want water to come out of their hot water faucets at temperatures greater than if it were just pumped through datacenters.

If I run water over the chips (lets assume fully submerged for simplicity) and maintain their temperature at 20 degC. ~100% of the heat is removed by the water.

Whoa whoa slow down there, Tex. You're still thinking in terms of conservation of energy. But there are entropy losses- how will you maintain the temperature at 20 deg C unless you're pumping loads of water across the chip- so much that the heat is dissipated across a volume of water too large to make any difference? Or if you're not- say you pump a low flow across the chip so it maintains a temperature at 30 deg C. A heat engine running on that potential difference (back to generating electricity for transmitting over these transmission lines) you won't be able to extract all the electrical energy that you needed to run the chip. Most of it will heat the great outdoors. But that's not what's going on- either in the article, or an imagined situation involving generation of electricity to go across power lines.

I realize there are line losses in the electrical wires. There are heat losses from the pipes piping away the heat. There are also radiation losses in the form of light and other waves that transmit through the water.

Yes yes I realize that too, but we're both waving that stuff away.

Re:WTF, why is a Carnot reference here?

[MillionthMonkey]

Yeah I read too fast. Although when I was a kid I used to have a Finnish pen pal in Turku. She stopped writing.

Re:WTF, why is a Carnot reference here?

[daremonai]

There is NO WORK being done.

You know way too much about computers.

Re:WTF, why is a Carnot reference here?

[pookie13]

Yeah I read too fast. Although when I was a kid I used to have a Finnish pen pal in Turku. She stopped writing.

No wonder she stopped writing if you thought that Helsinki is in Sweden. We do have a hate / love relationship with the Swedes.

I think it's great, but...

[natehoy]

Is pumping boiling water through pipes the most efficient way to heat houses? Isn't there a pretty massive heat loss in the pipes?

Having said that, if they are already using this system for heat, the introduction of waste heat from a datacenter seems to make a lot of sense. Acts as a heat sink for the data center, reduces the amount of energy needed to heat the water.

Re:I think it's great, but...

[onionman]

Is pumping boiling water through pipes the most efficient way to heat houses? Isn't there a pretty massive heat loss in the pipes?

Having said that, if they are already using this system for heat, the introduction of waste heat from a datacenter seems to make a lot of sense. Acts as a heat sink for the data center, reduces the amount of energy needed to heat the water.

Actually, it's a reasonable system for heating large building complexes where a central facility can heat the water. Many Universities and large corporate complexes already use similar methods for heating their campuses. Insulation on the pipes keeps the water warm in transit. These complexes can also cool their buildings in the summer by pumping chilled water through the system.

Re:I think it's great, but...

[sfcat]

Yes and no, water actually is a very good "thermal" battery. That is why coastal regions have a more temperate climate than inland region. Its cheap and we know a lot about how to move it around and have existing infrastructure for doing exactly that. Its not the most efficient way, but often it is the most practical and economical.

Re:I think it's great, but...

[vertinox]

Its not the most efficient way, but often it is the most practical and economical.

Also, if the pipe breaks, then its not really that bad of a cleanup.

Re:I think it's great, but...

[sjames]

It depends on the priorities and the source of the heat. Steam turbines have a considerable load of waste heat that has to be dumped somewhere. No sense heating a lake if it can heat homes instead. Since it is waste heat, the efficiency hardly matters, any usefulness beats the alternative.

In other cases the choice is between many small boilers or one big one with exhaust scrubbers and more complete combustion. With good pipe insulation that can be a win.

Valium and Xanax for Engineers and Physicists

[NoYob]

The pump is also very efficient -- you get five times the amount of energy you put in, he said.

So, engineers and physicists, when you see statements like that, how do you cope:

1. Stiff drink(s)
2. Xanax(s)
3. Dust off plans for your perpetual motion machine company to go public
4. Cry yourselves to sleep.
5. Other

Re:Valium and Xanax for Engineers and Physicists

[rockNme2349]

6. Post condescending comments on a forum that no one will read.

Re:Valium and Xanax for Engineers and Physicists

[JessGras]

Heat pumps can be this efficient when you consider the claim is they can move five times as much (heat) energy as they consume (in electicity or other organized source). They are not claiming to generate more than they consume: only pump more than they consume - though vague and sensationalist phrasing in the journalism makes this unclear in the OP.

Re:Data center cooling in the winter

[afidel]

That's correct, in many climates you would spend more energy trying to maintain humidity then you would save by not running the AC system. For larger systems many have a "freecool" option which runs the waste stream through the heat exchanger without running the compressors thus saving ~80% of the energy.

That's good

[Yvan256]

"Honey, why are you watching so many porn streams at once?"
"Because I'm cold!"

It IS great

[dgr73]

Not to mention that when you have hot water coming out of the pipes, you don't need a water boiler, which is something all houses without kaukolämpö (remote heat) need. All in all, the infrastructure is in place in many places in Finland, with insulated pipes dug deep enough into the ground to keep the heat, so why not take advantage of it.

Obligatory

[interiot]

"The Internet is not a big truck. It's a series of tubes. And if you don't understand, those tubes can be filled and if they are filled, when you put your message in, it generates more heat and it's going to be delayed by anyone that puts into that tube enormous amounts of boiling water, enormous amounts of boiling water."

Re:Data center cooling in the winter

[djrok212]

This already exists, and is in use in many data centers, they are called Air Side Economizers, http://www.42u.com/cooling/air-side-economizers.htm

Forced air is too dry

[mi]

Well, they have to be, because you're basically threading a steam bomb throughout your entire house. I'll stick with forced air thank you.

Forced air will dry you into a raisin. It is December — do you notice, how dry your lips are in the morning?

You need humidifiers to fight that effect... No, hot water — pumped through fixtures made of cast iron, or something, that's even slower to warm up and cool down — is the best heating solution... It could be expensive, but it is the most comfortable of what's commonly available today.

The oft-used copper and/or aluminum fixtures are bad, because the temperature will be fluctuating widely between the times, the heat is turned on by your thermostat and the times, when it is off. Our bodies are more sensitive to changes in temperatures, than to the temperatures themselves. Also, a quickly-heating material ends up losing heat mostly through convection (heating up air, that rises to the ceiling), than through radiation, which warms you directly (via infra-red).

Stainless steel is better in that regard than copper/aluminum, but not as good as cast iron, heavy and "unattractive" as those things might be...

What about the exec office?

[filesiteguy]

Now that we have the issue with the heat coming from the server room solved, let's tackle the hot air coming from the executive offices next.

Any ideas?

Heat Recovery Ventilation

[Doc Ruby]

Common commercial devices for homes already use heat exchangers to recover 66% or more of heat from vented air, heating the incoming fresh air with it. During heating seasons, machinery's inefficiency generating heat can replace heat that would have consumed more energy. Bathroom fan vents cost under $300.

What we need is good heat storage devices. If a lot of heat can be stored during the cooling season, and released during the heating season, these electrical devices become close to 100% efficient. Places like Helsinki have much longer heating than cooling seasons, so they're good places for datacenters that can recover heat for use.

The problem is that water is about the densest heat storage material we have, but it doesn't store very much. And even the most cutting edge insulators, aerogels, are only about 2x as insulating as the current common top performers, closed cell foams, and only about 4x as insulating as the earlier common stuff like fiberglass and cellulose. If we could store in similar volume the energy that fuels like oil store in chemical covalent bonds instead in physical materials like high specific heat fluids that don't get that hot, we'd have a lot more options in engineering efficiency. If we could regenerate chemical fuel from heat at very high cycle efficiency, we'd have something of a miracle cure for many of the worst of our industrial ills.

Re:Space Heater

[smoker2]

I have a power brick under each foot. Toasty !