What is a Smart Meter?
A Smart Meter measures electrical energy consumed (kWH) over a specific period of time. Unlike current meters that simply accumulate total kWH consumed Smart Meters are able to report how much is used between specific times of the day. The intervals of time could be hourly or blocks of hours to correspond to when electrical prices are most likely to be high or low. This is called Time of Use metering and billing.
Who will get a Smart Meter?
All customers who currently have a simple kWH meter and are billed on total kWH used will receive a Smart Meter. The Ontario Government has mandated that all these customers in Ontario are to receive a Smart Meter by the end of 2010.
How can I use Stata to calculate power by simulation?
First, the general procedure is Use the underlying model to generate random data with (a) specified sample sizes, (b) parameter values that express the difference one is trying to detect with the hypothesis test, and (c) nuisance parameters such as variances. Run the Stata estimation program (regress, glm, etc.) on these randomly generated data. Get the parameter estimates and standard errors using e(b) and e(V). Calculate the test statistic and p-value. For example, if it is a z-test, divide the parameter estimate of interest by its standard error and use the normal() function to get the p-value. Specifically, suppose b is the coefficient estimate with standard error sb. The two-sided p-value to test the hypothesis of a zero coefficient is then equal to 2[1−phi( | t | ) ], where t = b/sb and phi is the standard normal distribution function returned by normal(). Do Steps 1?4 many times, say, N, and save the p-values in a file with N observations. The estimated power for a level alpha test is simply the proportion of observations (out of N) for which the p-value is less than alpha. WARNING: If there are covariates, make sure they remain fixed throughout all N iterations of the simulation! Do not regenerate them each time. NOTE: As a check, always run the simulation for the null case to make sure the power comes out to be alpha (to within the sampling error of the number of iterations). More generally, in the null case, the distribution of the p-values should be uniform. This may be easily tested in Stata using the ksmirnov command. Now an example: We wish to test the effect of a drug dose on a Poisson-distributed response y in rats. For a sample of n rats, we have the Poisson regression model log mui = b0 + bixi (i = 1,2,…,n) y ~ Poisson(mu) where xi is the dose in milligrams. given to the ith rat. Suppose we are trying to decide what sample size would give reasonable power for the test of the null hypothesis b1 = 0 if the true value of b1 were 0.65 (the alternative hypothesis), under an experimental design with three levels of dosage (0.2, 0.5, and 1.0) repeated r times on n = 3r different rats. The following program estimates the power for a fixed value of r. One can then run it for several values to arrive at an r of choice.
FAQ: AC vs DC Power
Why is AC power currently the industry norm? What are the benefits of switching to DC power?
Thomas Edison originally promoted DC for electrical power distribution, considering it a safer, more reliable option than AC power. Edison faced off against Nikola Tesla and George Westinghouse in the ensuing ?Current Wars.? AC ultimately came out on top due to technological limitations of the time. AC had the advantage back then of being stepped up to high voltages by using transformers, sent via thin, inexpensive wires, and eventually stepped down again at distribution to the user site. Still, DC power has continued to be used in high voltage scenarios, as well as in low voltage deployments in the telecommunications industry and light transportation industry. Today?s technology, however, enables users to leverage the advantages of DC power. As Edison realized, DC power represents a more stable option. Unlike the sine wave of AC, DC electrical charges flow in the same direction at a constant. This quality allows DC systems to not only offer greater stability (less equipment needed to synchronize sine waves), but also to enable easier integration of multiple power sources, since backup (or primary sources) such as photovoltaic, flywheels and batteries all produce energy in the DC format. Additionally, current AC systems require a series of power conversions that result in energy being released in the form of heat, which then must subsequently be cooled. This power and cooling challenge has become a serious issue in the data center industry, with 85% of data center organizations currently taking steps to address energy costs, according to a recent Ziff Davis study. The benefit of DC power includes a reduction in the number of power conversions, and therefore a reduction in cooling requirements. Is DC power reliable? Yes. In fact, the Lawrence Berkeley National Labs (LBNL) performed a demonstration project in 2005-2006 that was essentially a bake-off between traditional AC power distribution design and DC power distribution design, and the findings supported claims that DC power is reliable and energy-efficient. According to the results of this project, DC power not only saved as much as 28% in power consumption, with additional savings fostered by an overall reduction in cooling, but DC power was also found to be much more reliable than traditional AC power. Furthermore, DC power is currently used in mission critical systems in nuclear power plants, subways systems and even the phone system.
Is DC power safe?
Yes, DC power can be used as safely as AC power. Specifically in the case of the Validus offerings, the unique Validus system steps down the high voltage energy that comes in from the utility grid and ultimately converts it to a ?touch safe? -48 VDC, which is then distributed from the row to the rack. This -48 VDC meets Safety Extra Low Voltage (SELV) levels, which means that a user can safely come into contact with this level of voltage without risk of electrical shock. Also, the core component of the Validus system – the converter unit – is certified to CB scheme EN-60950 safety standards which is recognized by the NEC, NETA and UL Codes and Standards that are in place for the telecommunications industry.
If I decided to deploy the Validus DC power system, would I have to replace my current AC systems? The Validus DC power infrastructure is designed to work alongside legacy AC systems.
Customers would not need to ?rip and replace? their prior investments; however, they may decide to eventually migrate from the lower-density, AC infrastructure to the higher-density DC model. This migration can be part of an overall retrofitting approach as Facility Managers continue to refine their data center’s processes.
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