Monthly Archives : February 2017

My Perfect Green Data Centre (3) – AC/DC

AC/DC is not the name of the rock band, nor an allusion to anything regarding sexual preferences.

As I said in my last post, electricity consists of electrons in motion. However, there are two basic modes of motion: coming and going, or plain going: Alternating Current (AC) and Direct Current (DC). There’s pretty comprehensive wiki article on AC here.

Why should this matter? Simple. Data centres put electricity to two fundamentally different types of work. The first type of work is IT. All IT runs on DC. Just because it’s got a 110V/230V AC socket at the back doesn’t mean it consumes AC. The first thing the computer does is convert the AC to DC.

The second work to which electricity is put is cooling. There are quite a few technologies for this, and the optimal technology depends on the size of the data centre and the climate, but they all boil down to the same three types of components: heat exchanges, pumps and fans.

Why does this matter? After all, we’ve been converting AC to DC on an industrial scale for over a century, and, since the advent of the switch mode power supply, the conversion loss from AC to DC is tiny.

Here are a few reasons:

  1. Photovoltaics generate DC, not AC. Converting DC to AC has never been as efficient as the other way around.
  2. Batteries produce DC.
  3. Industrial scale pumps and fans are much more efficient with AC (3-phase) than DC.
  4. In order to get really green, we need to get really efficient. All the easy wins have been won; we need to look at the margins to find those remaining gains.
  5. Engineering excellence.

So, in the next part(s), I’ll look at the DC part. I’ll move on to the AC part when I’ve finished with that.

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My Perfect Green Data Centre (2) – Storing Energy

The idea is to build a clean data centre: less energy, cleaner energy, and fewer nasty things. As the first two concern energy, I’ll first set the scene on what energy is.

Data centres are energetic beasts. They not only consume huge amounts of energy, but must also store huge amounts of energy. The obvious example is the battery pack of a UPS system, but that diesel fuel in the tanks for the generator sets is also a form of stored energy, and air-cooling systems are full of pockets of stored energy, too.

Energy takes many forms, but the form which computers need is electrical. And this is the first difficulty with data centres. Nature is set up to store heat, movement (kinetic) energy and so forth, but not for storing electricity. Take heat. The atmosphere which protects this planet from the frigid reaches of interplanetary space is a natural heat storage system, and the rock crust of Earth which keeps the mantle contained, another. A vacuum flask is not natural, but it’s cheap, easy to make, and stores heat.

Another form of natural energy storage is kinetic. Set a (fly)wheel in motion and, absent of friction, it will spin until the end of time. Kinetic storage can also be combined with gravity: lift something up using kinetic energy, and the energy used to lift it will be stored until that thing is dropped. (As one of nature’s clumsier individuals, I often see downwards kinetic energy realized by the breakage of a cup.)

Electricity is an altogether different beast. Electricity is free electrons in motion. For those who remember school chemistry, atoms consist of a nucleus of protons and neutrons, surrounded by outer shells of electrons. Those electrons spin round and round the atom. So, in a sense, potential electricity is everywhere – in the pages of the books in the shelves to the right of where I sit typing, in the precarious cup in front of me. But, in the other sense, it’s nowhere, because like people, electrons are creatures of domesticity. They only leave if pushed; they don’t just wander away.

When an electron is knocked off its atom, it seeks a home. To do this, it must move and, when it does this – and only when it does this – does it become electricity. Hence the problem: you can’t store things that are moving.

Nature, therefore, doesn’t store electricity per se and neither do we. We convert electricity to another form, and convert it back again when we need it. The predominant ways of doing this are electromagnetic induction, photonic bombardment, and the quantum equivalent of a foster home.

Induction (I won’t pretend a detailed understanding of the physics) is the traditional method of generating electricity: stored or generated kinetic energy is used to turn a turbine, which in turn rotates a magnetic field in a dynamo or alternator, which produces electricity. Turbines are turned indirectly by steam by burning coal, oil, LPG, diesel, recycled waste and creating sub-critical masses uranium, and directly in hydroelectric plants and wind turbines.

Photonic bombardment is the essential physics behind all photovoltaic (PV) cells. Photons, those bearers of light - mostly from the sun but in principle from anywhere – knock the electrons out of their homes.

The foster home is the battery: an electron is given temporary accommodation on the outer ring of an atom that doesn’t really want it, and runs free as soon as it’s offered a place to go.

So, that preliminary out of the way, on to where it all starts: the back of the computer.

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My Perfect Green Data Centre (1)

This is the first of a number (I don’t know how many) of posts on how I’d set about building the perfect green data centre (and “green” doesn’t refer to the colour of the paint).

First, a little about me. I’m an Uptime Institute Accredited Tier Designer (no 1837), and one of the very few ATDs who has an IT rather than an engineering background. I started my career when I was thirteen, soldering together brick and bat tennis games. Within a year, I’d graduated to a 6502-based Commodore PET, and have been hooked ever since. After a patch of software, I rekindled my hardware roots and moved into IT infrastructure. I’ve assessed dozens if not hundreds of data centres on behalf of my clients, I’ve moved clients in and out of data centres, and I built the Arabian peninsula’s first Tier-4 data centre (though it never was certified).

I live and work in South-East Asia. Most of SE Asia is under-serviced with data centers, but a sixth the Earth’s population lives here. Therefore, lots of data centers are waiting to be build. But SE Asia presents challenges that are not present in North America or Europe. Supernap, for example, have huge campuses in Reno and Las Vegas. But there, the temperature and humidity is within ASHRAE A3 limits for nearly every day of the year – what cooling they need, can often be provided with fans.

In SE Asia, in the tropics, it’s either chucking down rain with humidity in the 90%+ range, or it’s the dry season and temperatures soar through the 40C mark. So the trajectory that’s been taken in the developed world, although it can be made to work, won’t produce optimal results. Given just how many data centers are likely to be build in the next decade, and the enormous potential for them to be nasty and polluting, there’s an urgent need to re-think how we build them.

The industry as a whole is well aware of green concerns. But most of those come down to energy efficiency. The IT load is taken as given, and the focus is on minimizing the load around that, mostly cooling. This leads to the standard industry measure of efficiency, the Power Utilization Efficiency or PUE. The industry is aware that there’s more to it than that, but has yet to come up with benchmarks that include how clean the power is (coal-generated electricity being the dirtiest and renewables the cleanest), or the carbon footprint of building the data center itself.

So my concern is broader than PUE. I am concerned about:

  1. Energy efficiency
  2. Source(s) of the energy
  3. Minimizing the use of substances that have nasty environmental effects

And this, within the context of providing predictable availability in a secure environment.

I hope this blog will not become another guy spouting off into the void of cyberspace. I’m open-sourcing my ideas in the hope that someone out there – Tim Cook? Mark Zuckerberg? – hears of them and decides to build one of my perfect green data centers. I’d like to give them the best possible, and for that, I’d love feedback, improvement and, above all, corrections.

A final point. I do not claim that my ideas are original in the sense that no one has had them; that I am the first to have them. Where I find that someone else has had the same idea, I will attribute it. All I claim is that the ideas here are original in the sense that I had them independently.