Hard Choices

Posted on June 7, 2011 // Leave a Comment

Between An (Energy) Rock and A Hard Place

Just as concerns about global warming and carbon emissions were about to create a rejuvenation of nuclear power, the Tohoku earthquake and tsunami rocked the shores of Japan, and with it, the latest nuclear renaissance.

This recent disaster in Japan has shown us that we are increasingly stuck between a rock (coal) and hard place (nuclear fuel rod) when it comes to energy sources. If we’re going to solve this conundrum, it’s time to take another look at the cost comparison between generating energy and conserving energy, or negawatts. A negawatt is the opposite of megawatt – a million watts of power avoided versus a million watts of power used – a powerful concept with demonstrated ROI, that even the Federal Energy Regulatory Commission (FERC)* has now recognized.

Consider the following cost estimates for new power generation from the most common sources, drawn from information supplied by the Energy Information Agency (http://www.eia.doe.gov/oiaf/beck_plantcosts/index.html), which cites “overnight” costs. An overnight cost is the physical construction cost of the plan, divided by capacity, and does not include land costs, financing cost or any other related cost.

Nuclear: Even before the disaster in Japan this year, the EIA estimates overnight cost of a nuclear plant at $5,335/kW.

Coal: The same EIA report lists the overnight cost of a coal-fired plant as $2,884/kW without carbon capture and $5,388/kW for integrated gasification combined cycle with carbon capture.

Natural Gas: The EIA lists the overnight cost of a natural gas plant at $978/kW for a conventional combined cycle plant, and $2,060/kW for advanced combined cycle with carbon capture (NGCC with CSSS).

Conservation: I estimate that an energy efficiency project with a simple payback of three years under an electric rate of $0.0982/kWh (the average retail price in the U.S. according to EIA; http://www.eia.doe.gov/cneaf/electricity/st_profiles/e_profiles_sum.html) has an equivalent “overnight cost” of no more than $2,581/kW. This figure assumes that the energy savings accrue over all 8760 hours of the year. If the savings accrue over fewer hours, then the equivalent “overnight cost” would be lower because the kilowatt reduction would be higher. The calculation is simply the electric rate times the hours per year of operation, times the simple payback period in years.

Conservation with a moderate payback period is roughly the same cost as the cheapest clean generation technology (NGCC with CCS) and, since many conservation projects have a much faster payback than three years; this leads me to the following proposal:
“As a society, we should stop funding the construction of any power plants in the U.S. until we have engaged and exhausted all conservation projects that have a payback of less than three years. We should finance the overnight costs of these conservation projects via a savings charge on individual energy consumption. Each end-user’s savings charges would go into that end-user’s energy savings account, which they could use for their own energy conservation projects. If the funds aren’t applied in a reasonable amount of time (e.g. three years), the end user loses them. The savings charge rate, as a fraction of a utility bill, should be set so that societal savings charges equal the current rate of spending on new power plants.”

In my view, this will force a more through analysis and comparison of the effects of conservation versus construction, and lead to a more efficient use of capital in energy generation. At the same time, it will have the important effect of contributing to a reduction in greenhouse gasses and spent nuclear fuel.

In the coming months and years, the Japanese will undoubtedly teach us a great deal about how effectively aggressive conservation can help to quickly offset the loss of power generation capacity. And I suspect that what we will learn will be consistent with this proposal.

*http://www.ferc.gov/EventCalendar/Files/20110315105757-RM10-17-000.pdf

Filed Under: Data Centers //

Avoiding Risk

Posted on April 4, 2011 // Leave a Comment

Avoiding Risk in Data Centers Sometimes Means Counter-Intuitive Thinking

Sound data center risk mitigation practices can also lead to energy cost savings. But sometimes the route there is counter-intuitive.

Always-on, always-cold is still a commonly-used strategy for data center cooling operations – and for good reason. This type of operation is fairly easy to implement and monitor, and running all the CRACs all the time logically reduces the risk of downtime should a unit fail.  In this operating strategy, the CRACs are run at a low set point.   They operate at  lower than required temperature to mitigate the risk of hot spots or to add ride-through time in the event of a cooling system failure.

While this seems a logical and prudent practice, if you dig a little deeper, you’ll see that it’s not quite as risk adverse as it initially appears – and, more importantly, it misses a larger opportunity for significant energy cost savings. Let’s examine each practice individually.

Continuous operation of all CRACs, including redundant (backup) CRACs, wears all units out prematurely. Increased runtime for any piece of equipment that wears out with use naturally reduces its lifecycle.

Leveling CRAC runtimes, in which each CRAC is set to run approximately the same number of hours, has the same issue. This practice might extend the time to first failure; however it also increases the risk of catastrophic failure (i.e. simultaneous failure of all units).

And then there’s the issue of low setpoint thresholds.  Common thinking regarding cold operations is that an overall cooler temperature will use the thermal mass of the infrastructure to provide extra time to react in the event of a cooling system failure.  However, when all CRACs operate equally, each CRAC runs at a lower (less efficient) utilization, meaning that the discharge air from each CRAC will be higher.  Some CRACs, in effect, may not be cooling at all, which means that in a raised floor data center, those that are not actually cooling are blowing return air into the underfloor plenum.  Since the largest source of thermal mass in a data center is the slab floor, this means that this ”always-on”, and/or low set point approach to CRAC operation may not yield the best utilization of thermal mass.

A “just-needed” operation policy is preferable in terms of both catastrophic risk mitigation and energy efficiency.  In this case, the most efficient CRACs are operated most of the time, and the less efficient CRACs are kept off most of the time – but held in ready standby.   Even when CRACs are nominally the same, there can be significant differences in their cooling efficiency due to manufacturing variability.  These differences, if measured or characterized, can be utilized to further optimize efficiency and mitigate the risk of catastrophic failure.

Sometimes the obvious or even most commonly used cooling strategy isn’t the best strategy, particularly as rising energy costs become more of a concern.   An operating strategy that recognizes and anticipates the possibilities of “little failures,” while focusing on the avoidance of catastrophic failure and reducing energy costs, is not only forward looking but also represents best practice.

Filed Under: Data Centers, Technology //
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