Friday 30 March 2012

Queuing for fuel at UK filling stations.

One of the UK trades unions (Unite) has received member approval from the fuel tanker drivers to call a strike in respect of deliveries of fuel to filling stations for Diesel/DERV and/or petrol/gas. By law the union has to give five days advance notice of the actual strike dates, but so far they've not been announced.

Some ill judged comments by a couple of government ministers has prompted the public to rush out and top up their vehicle fuel tanks prior to the strike. In some cases people are filling fuel cans with additional spare fuel, in the case of petrol if it is badly stored it can increase risk to the family home. On the whole I think that keeping the fuel tank well topped up is a good precaution in advance of a potential strike.

Unfortunately the public commercial fuel distribution system for petrol (gas) and diesel is a fragile model based on the "just-in-time-delivery" system which may reduce supplier costs slightly, but which has little resilience to a surge in demand or a sudden interruption of delivery. The filling stations only hold 2-3 day's supply of fuel in their storage tanks and depend on regular timely delivery by tanker lorries. The public know this and want to avoid the inconvenience of not having fuel for their vehicles so they take the next opportunity to top up with fuel which exacerbates the limited fuel supply problem. In this morning's news it is reported demand for petrol is 172% of the norm on 29th March 2012.

The filling station managers attempt to reduce the flow of fuel from their limited local storage tanks by shutting off most of the filling pumps on their forecourts. As anyone with a rudimentary knowledge of queuing theory knows reducing the number of service points for a single queue tends to lengthen the queues. As a consequence the whole thing spirals into a worsening situation, though in the longer term the overall amount of fuel consumed by motorists doesn't actually alter.

The whole situation would be considerably eased if the owners of filling stations were forced by legislation to routinely hold ten times the average daily fuel sales in their local storage tanks. In effect increasing the capacity of the system to withstand short interruptions to the supply chain. The cost would be a few pence per vehicle driver. In effect the interest payable on seven days fuel, even less if the tax system was altered to be charged when fuel is dispensed rather than when it is delivered. The suppliers blame the motorists for demand variation when in fact it is the suppliers who create the problem in the supply system.

Regular readers may be asking how this affects the operation of a trading floor/data centre which the normal focus of this blog.  Firstly there is the risk to the top up supplies of diesel to the standby generators. If tanker drivers are either on strike or are servicing public filling stations in preference it is a risk to your business. Secondly the fuel situation could affect vehicles of key personnel or delivery vehicles. Maybe the assumptions of availability of replacement fuel for your business are not valid, regardless of any contractual commitment by your suppliers. In the absence of a resilient national infrastructure for fuel supply it may be worth considering alternatives such as increased or dispersed fuel storage, perhaps even providing fuel to key employees vehicle during a national fuel supply crisis.

Here's another list of useful points to consider.

Wednesday 28 March 2012

Cheaper Photovoltaic Power?

3D stack of photovoltaic cells. Increase output by 20x

Cheaper production of silicon photovoltaics.

Edit 30th March:
Amazing! I posted the above two links really as a memo to myself to do more research into these technologies Yet I've had loads off people reading this page. Must be hot stuff!

Wednesday 14 March 2012

Efficient combined cooling - Turbomiser

As you can see from the recent blogs, a couple of weeks ago I visited the Data Centre World exhibition. I've suffered a few days outage thanks a cold caught from a stupid woman who sat next to me on the train home, but finally I've been able to complete research into one of the devices I saw at the exhibition.
The device was the Turbomiser which was presented by Klima-Therm. The Turbomiser is a compact self contained chiller unit which weighs in at a relatively light two tonnes. It makes good use of recent developments in efficient chiller technology to gain from cheaper methods of cooling when climate conditions allow. The core of the unit is an intelligent controller (Geoclima Microsmart) which coordinates the mechanics to use the most efficient method of cooling. When free air cooling is available the Turbomiser will make maximum use of that. Where external air conditions permit, evaporative cooling is automatically used to reduce the cooling load on the chiller compressor. The compressor built into the unit is the highly efficient Turbocor twin rotor unit.  The heat exchange panels are constructed using micro channel aluminium which give good efficiency while reducing the amount of refrigerant required.

The combined technologies lead to greatly reduced operating costs with payback period of 2-3 years. The unit looks to be a good option if you are in the position to install new or refit an existing installation.

The evaporative cooling does not use aerosols sprays to cool, but moistens evaporative panels. Air flowing over the panels is cooled by evaporation of the water. Avoiding the use of sprays and the lack of standing water avoids the risk of Legionella  infections.

Friday 9 March 2012

Resilient power housed in a shipping container

One more power item from the Data Centre World show that piqued my interest was the Advanced Diesel Engineering Ltd "plus one" continuous power unit. They've squeezed a pair of Volvo (2 x 410KVA) diesel generators, a pair of fuel day tanks into a "shipping container". They have a combined output of a shade over 800 KVA or 400 KVA in a resilient ( 1+1) configuration. They have a five hour endurance on the just the day tanks.

From my casual inspection it looks well designed and well constructed and ADEL have been in this business for some time.
The total self contained unit weighs about 13 tonnes wet weight and has a footprint of 6 x 2.4 metres. The standard silencing yields 75 dB(A) at 1 metre when both engines are on full load.  The unit is essentially plug and play.  If you have the need for an easy installation for 400 KVA of back up power and can handle the site placement of a shipping container, then this may be the solution for you. Do lock it down well though, they have a very similar unit on special offer at £140K at the moment.

Riello do a similar unit which they call "PowerBox", but this has a single diesel motor coupled with a rotary UPS.

Monday 5 March 2012

Air Battery UPS

An interesting technology at Data Centre World was the Air Battery. It is a system designed to provide 30 seconds of uninterrupted power to a Data Centre electrical power UPS system. The technology uses stored compressed air to drive fast starting in-cabinet expanding scroll rotors. Ultra capacitors are used to provide energy during the brief start up time of the scroll rotors. The  endurance of the Air Battery can be extended by use of additional stored compressed air tanks.

The advertised power ranges are from 3KW right through to 3MVA. The technology has been deployed in National Grid environments, so it is no lightweight technology struggling to find a market. The units depend on having a fast start generator to take up the power load as the air supply depletes. To facilitate fast generator start up, heat from the air battery can be used to pre-heat the diesel motor. Such diesel generators need to be kept at 35 degrees Celsius to aid fast starting. When the air battery is triggered and producing power there is a by-product of cold exhaust air which can be used to contribute to the cooling of a data centre while the air conditioning await the power from the standby generator..

The manufacturers claim lower operating costs, lower maintenance and greater reliability over a stored energy rotor system because there are no moving parts until the scroll rotors are activated. (excepting recharge compression of the air storage tanks.  Bearing friction, air friction and even the centrifugal effect of the earth's rotation can affect the storage efficiency of a rotor system.

Similarly this system is claimed to have a a lower ongoing operational and maintenance cost when compared with a lead acid battery power stage system. Batteries need a trickle charge to maintain power over long periods. In the case of gel acid lead batteries there is a cost a relatively short life. If you keep the gel acid battery cool it should give a five year lifetime. Wet acid batteries can survive 10 - 15 years depending on their construction and storage conditions. If the ambient temperature in the battery room is allowed to rise over 20 degree Celsius (about 70 Fahrenheit) the battery life will be shortened. So there is also an implied air conditioning cost unless free cooling can be used.Wet acid batteries generally need a specially constructed secure room with good ventilation, temperature conditioning and an acid proof tanked floor.

We managed one trading floor data centre implementation where the lead acid batteries had to be located away from the UPS power unit by reason of the weakness of the floor in the Data Centre Room. We had to install a very thick copper cable to take the low voltage power from the batteries to avoid too much voltage drop before it reached the UPS unit. Going from the basement to the fourth floor meant we were working at the absolute low voltage power cable length recommended by the manufacturers of the UPS. If we'd been able to use a compressed air battery we'd have been able to use much longer compressed air pipes.

Friday 2 March 2012

Standby generator fuel contamination

I paid my annual visit to Data Centre World in Olympia London yesterday. Several items caught my attention. One of those was the IPU Fuel conditioning stand. I'd read about the "diesel bug" problem a couple of months ago but not really paid much attention, but it could be an important issue for Data Centres/businesses which depend on diesel powered standby generator for their electricity backup. This may be an issue which IT managers think is purely a responsibility for the facilities manager, but at the very least they should ensure that their FM colleagues have considered the issue. Similarly if your business operates in a multi-tenanted building it may be appropriate to ask the Landlord how they approach this matter.

Essentially the diesel bug is contamination in diesel fuel arising from bacterial, fungal, yeast growths which can grow in water contaminated diesel. The diesel bug can grow in to a mat which floats between the interface of diesel/water layers. The mat can also form as a plaque on the inner surface of the diesel tank, pipework and filters. If that mat is disturbed chunks can float off and be sucked into the fuel filters of a diesel motor, such as a standby generator. In a way it is a bit like the diesel engine is having a heart attack as essential feeds are blocked. The by-products of the diesel bug can also create acidic conditions which can corrode metal tanks and fittings.

If the fuel filter of  diesel motor becomes clogged with contaminants the motor will be starved of fuel and cut out. This is not a good thing if there is no mains power and your data centre is depending on the standby generator. Even in N+1 resilient generator configurations the risk is high if the fuel is contaminated.

Diesel fuel in the UK can contain up to 7% bio-diesel. Bio-diesel is hygroscopic, which means it is prone to absorb water vapour from the air. In the diesel storage tank this absorbed water can separate out in to the base of the tank, potentially leading to the diesel bug. If the water reaches the injectors of the diesel engine it can cause serious damage to those injectors.

IPU were offering fuel polishing units which can be installed, either permanently or as a mobile unit, to remove contaminants, such as water, from the stored diesel in the fuel tanks of a standby generator. They also provide assistance in testing the fuel to detect contamination and bacterial growth. The stagnant conditions of a standby generator fuel tank could mean that the problem of the diesel bug in your fuel does not become apparent until you most need the generator for an extended period of operation. Short monthly test runs might only create only minor disturbance in the fuel tank, but a longer term run in a live regional outage could see your generator failing and sustaining serious damage.

The fuel polishing technique could also be used to avoid the potential problem of contaminated fuel being delivered by tanker to your main tank during a period of extended mains power outage, such as a regional power outage. One solution may be to deliver the fuel to a holding tank, polish it and test it before releasing it to the main fuel tank(s). The equipment required to polish the diesel is not terribly expensive, it is a technology which has been around for some time in the maritime and transport industry.

I'll certainly be adding this topic to the check list of questions I use when auditing a data centre site for physical security. It is a risk factor that can be avoided.

There is a short video of the IPU system in operation:

Here's another useful blog site on generator issues.