How much is a kWh?

Hello Readers,

As I was writing my series on Net Metering, it was pointed out to me that most people are not especially familiar with some of the units that I used in the article. Thus, in this post, I would like to offer a primer on units that are commonly used when talking about electricity (and how they relate to renewable energy and energy use). At the bottom of this post, I have also included a glossary of Energy Industry Terminology that you may encounter while reading about renewable energy and energy use.

What's a Watt?

A Watt (W) is a basic unit of power measurement. Watts are used to measure how quickly energy is consumed by or generated by a system.

But what about all of the prefixes?

Unit Name	Abbr.	Meaning	At This Scale
Microwatts	μW	1/1,000,000th Watts	Wrist Watches
Milliwatts	mW	1/1,000th Watts	Laser Pointers
Watts	W	1 Watt	LEDs
Kilowatts	kW	1,000 Watts	Average US Households
Megawatts	MW	1,000,000 Watts	Aircraft Carriers
Gigawatts	GW	1 Billion Watts	Medium Size Cities
Terawatts	TW	1 Trillion Watts	Large Countries

Note: whether a prefix is capitalized or not can alter its meaning in some cases.

How about a Watt-hour?

A Watt-hour (Wh) is a basic unit of energy measurement. Watt-hours are used to measure how much energy is consumed by or generated by a system.

1 Watt-hour is the amount of energy that would be consumed by or generated by a system if the system operated at power level of 1 Watt for a time period of 1 hour. Note that, all of the prefixes listed above apply to Watt-hours the same way that they apply to Watts (e.g. 1 kWh = 1,000 Wh).

Energy Used	At This Scale
15 Wh	Compact Fluorescent Bulb for 1 hour
250 Wh	Xbox 360 and LCD Television for 1 hour
1 kWh	Average US Household for 1 hour
23 kWh	Nominal Rating of Electric Vehicle Battery
12 MWh	Average US Household for 1 year
20 GWh	Small US Town for 1 year
57 TWh	Total Massachusetts Electricity Consumption (2010)
3,750 TWh	Total US Electricity Consumption (2010)

Watts or Watt-hours?

Despite the similarity in name a Watt-hour is very different from a Watt!

For example, If I asked you, "How much power are the appliances in your house using right now?" Your response should be something like, "They are consuming 800 W."

Likewise, If I asked you, "How much energy do the appliances in your house use in a year?" Your response should be something like, "They normally consume about 9,000 kWh."

If you used the two units interchangeably (such as answering the first question as "800 Wh" instead of "800 W), it would be the same as confusing any other two units.

For example, if I asked you, "How fast were you driving when the cop pulled you over?" and you answered, "About 30 miles." In this case, your answer simply does not make sense!

Appliance Power

The more Watts an appliance is rated at, the more energy it consumes. You can think of this as describing how 'hungry' an appliance is. That is, how much energy does the appliance need to consume in order to do its job? In many cases, a higher power rating means an appliance can work more effectively. Of course, a higher rating does not necessarily mean that an appliance is doing a better job, sometimes it can mean a lack of efficiency. To put this in perspective, let me offer two familiar examples.

Example 1: Microwaves A 600 W microwave will typically take longer to cook your TV dinner than a 900 W microwave. In this case, the 900 W microwave is 50% more powerful than the 600 W microwave, which allows 50% more energy to be applied toward cooking your TV dinner each second that the microwave is running. In this example, the added power means the job is done more effectively. Example 2: Light bulbs A 100 W incandescent light bulb can often be replaced with a 25 W compact fluorescent light bulb and essentially the same amount of light will be provided. With each light bulb, enough light is provided to read a book each second that the light is turned on. In this example, the incandescent bulb is more powerful but less efficient, so a lot of energy is wasted by heating up the coils in the bulb.

Reading an appliance's power rating can also, sometimes, be a bit misleading. Some appliances - such as microwaves - have straight forward power ratings. (e.g. A 900 W microwave should be using 900 Watts of power when it is in use.) However, other appliances have power ratings listed that represent their maximum energy use.

Refrigerators, for example, are typically plugged in and 'turned on' all of the time, but a 720 W refrigerator is not constantly using 720 Watts of power. Instead, refrigerators may use their rated power for 5 minutes and then use no power for 25 minutes before switching back on again. In this case, a 720 W refrigerator would have a peak power consumption of 720 W and an average power consumption of 120 W (or 720 W x 5 minutes/30 minutes).

Generator Power

The more Watts a generation system is rated at, the more powerful it is. You can think of this as describing how 'strong' the generator is. That is, would energy being generated feel like a blast from a fire hose? Or, would it feel more like a squirt from a small water pistol?

Electric generator power ratings can also be a little tricky. For most types of generators (such as coal power plants, nuclear power plants, wind turbines, etc.), the so-called nameplate capacity indicates the maximum possible power generation under optimal conditions. However, solar photovoltaic (PV) generation systems can be especially confusing, because they have two nameplate capacities: an AC nameplate capacity and a DC nameplate capacity.

The AC nameplate capacity of a PV generator is relatively straightforward; it indicates the maximum AC power output that the system's inverter(s) can produce. On the other hand, the DC nameplate capacity of a PV generator indicates the expected cumulative DC power output for all of the solar PV modules under Standard Test Conditions (STC) without applying any derates, which in some cases compound to result in an actual output that is much higher than the DC nameplate capacity (see description below).

Solar PV Industry: Standard Test Conditions (STC)

In the PV industry Standard Test Conditions (STC) describe the production of a solar PV module at 25°C (77°F) at sea level with 1000 W/m² of incoming solar radiation (irradiance). While changes in atmospheric pressure can contribute minor changes in the actual output, changes in temperature and irradiance significantly alter the actual output of a solar PV module at different locations and throughout the year (and even throughout a single day). Depending on the location and time (and the amount of moisture and other particulates in the atmosphere) an array of solar PV modules may receive 100-1400 W/m² of solar irradiance during the daytime. This range includes irradiance both less than and greater than the STC irradiance. Greater irradiance will allows for a derate ratio that is greater than 1. Also, the cells in solar PV modules are better able to transfer electricity in cooler temperatures, which also allows for a derate ratio that is greater than 1. As a result, on a hot (cloudy) summer day a solar PV module will probably have  much lower output than the DC nameplate capacity. Conversely, on a cold (sunny) winter day a solar PV module is likely to have an actual output that is much higher than the DC nameplate capacity.

In any case, it is important to remember that the nameplate capacity of a generator is a nominal power rating, so it alone will not tell you how much energy a generator produces in a year. To determine a generator's annual energy production, you will need to multiply the nameplate capacity by the capacity factor and the amount of time in a year (i.e. Nameplate Capacity [W]x Capacity Factor x 8,766 hours = Energy Production [Wh]).

Other Terminology

Well, unfortunately, it would take an entire book or a semester course to explain all of the nuances of power, energy, voltage, and current related to energy generation and consumption. However, to help you along, I have put together a brief glossary of terms that are commonly used in the energy industry. I decided to put them in a logical (rather than alphabetical) order, so that you can read the glossary a bit like a book.

Glossary of Energy Industry Terminology

Nameplate Capacity	The maximum* potential power output or consumption for which a generator or appliance is rated to operate under optimal conditions (so called because this is often the nominal value listed on the name plate of the system).
Derate	A multiplier that describes what portion of a nominal system output remains intact after the effect of a non-optimal or non-standard condition is considered (often used to calculate the impact of changes in operating temperature or other environmental variables).
Capacity Factor	The Actual Power Output compared to the Nameplate Capacity over a period of time (typically as a %).
Availability Factor	The portion of time that a generator is physically able to operate (as opposed to being offline for maintenance; typically as a %).
Peak Power	The maximum amount of power that is actually generated or consumed during a defined period of time.
Average Power	The total amount of energy generated or consumed during a defined period of time divided by that amount of time.
Load Factor	The Average Power divided by the Peak Power for a defined amount of time (normally used to describe how well a utility grid is utilized; typically as a %).
Direct Current (DC)	Refers to power that is generated, consumed, or transferred at a steady voltage during normal operation (commonly used in batteries and solar photovoltaic modules).
Alternating Current (AC)	Refers to power that is generated, consumed, or transferred using a fluctuating voltage, which causes the current to alternate directions (commonly used in household appliances and long distance utility lines).
AC Voltage (VAC)	The voltage range over which AC power fluctuates (in the US, household electrical outlets nominally operate at ~120VAC, which means the actual voltage fluctuates between +120V to -120V many times per second).
Grid Voltage	Refers to the AC Voltage that must be maintained on a utility grid in order to ensure safe and reliable operation (neighborhood utility lines typically operate between a few hundred volts and several thousand volts).
Grid Frequency	Refers to frequency with which Grid Voltage fluctuates each second (in the US, household electrical outlets nominally operate at ~60Hz, which means that each second the Grid Voltage fluctuates through 60 cycles from +120V down to -120V and back up to +120V).
Inverter	A device that turns Direct Current (DC) power into Alternating Current (AC) power (a common component of solar photovoltaic generation systems).
Converter	A device that turns Alternating Current (AC) power into Direct Current (DC) power (often referred to as "AC Adapters" and are used in appliances and electronic devices that run DC power or rechargeable batteries).
Transformer	A device used to increase or decrease voltage (higher voltages are used to transport power over long distances with minimal losses; lower voltages are needed to operate common appliances).

*For solar photovoltaic modules, the Nameplate Capacity typically indicates the DC power output during standard test conditions of the module during its first year of operation.

I hope that you found this post useful. In the future, I will try to link to this post whenever I have included one of the terms listed above.

Cheers,

Sean Diamond

ColorPower - A Decentralized Smart Grid Technology

Hello Readers,

I hope you have been enjoying the on-going Global Sustainability series. This post is not in that series but instead is a weekend treat for the avid followers of this blog. Have no fear, the rest of the series is scheduled to post next week.



I was sitting in the lobby of an environmental non-profit the other week, and I happened to pick up a copy of the Spring 2012 issue of the MIT Energy Initiative's Energy Futures magazine in which I found an article about a new smart grid technology called ColorPower, which may be of particular interest for proponents of renewable energy, energy storage, and electric vehicles. The article, Tomorrow's power grid: Adjusting demand to meet supply (starting on page 11 of the magazine, page 13 of the pdf version), describes a 'smart grid' demand-side management technology that decentralizes the decision making process, giving the appliance users greater control over their electricity use and more privacy with regard to their habits.

I encourage you to read the article for yourself before proceeding any further. Here is the link again, in case you missed it: http://web.mit.edu/mitei/news/energy-futures/Energy_Futures_Spring_2012.pdf

I am particularly excited about this ColorPower technology, which is now being developed by Zome Energy Networks. As the article mentions, it could revolutionize the ability of homeowners to participate in their home energy use - especially with larger appliances. However, I think that it could also be (1) a key mechanism for electric vehicle charging and (2) a supplement and/or tie-in to energy storage devices.

In my dissertation (see the Background section), I specifically sought to avoid discussing energy storage devices that only worked in one direction (e.g. could only use electricity but not send electricity back to the grid), because on the electricity grid demand can be both too high and too low compared to supply. This is especially the case on a utility grid that includes a high percentage of renewable energy sources (such as solar photovoltaic and wind turbine generators). Thus, I was concerned that if I based the premise of my dissertation only on a technology that only had the ability to absorb extra energy when demand was lower than supply, I would be missing half of the equation.

During instances in which the supply is unable to keep up with the demand, the ColorPower systems could be used as envisioned by the system designer and described in the article - i.e. temporarily turning off or cycling down appliances based on the user preferences. In a mathematical sense, reducing demand is similar to sending more electricity onto the grid (the first half of the equation). However, I now believe that with the use of ColorPower or a similar technology much (but not all) of the role of bi-directional energy storage devices could be met with demand response, especially if it is used in combination with electric vehicles and thermal power systems.

If the ColorPower systems included a bi-directional switch, owners could not only elect to use less energy when demand is too high but could also request to use more energy when demand is too low. This may not seem practical when only considering traditional appliances. Instead let's consider non-traditional appliances such as electric vehicles and thermal mass systems (e.g. SmartBricks from Vcharge). In this case, appliance owners could prioritize their energy use so that it jumps (e.g. electric vehicles charge quicker than normal) whenever overall demand is too low and supply is too high .

As a result, if each building had some appliances set up to shutdown when demand is too high and other appliances set up to ramp-up use when demand is too low, each building could function in essentially the same role that energy storage devices filled in my dissertation. This sort of bi-directional demand response could also avoid some of the trouble with V2G systems that require EV batteries to be less than fully charged in order to function.



Well, that is all for now, I hope that I have provide you with enough links to keep you busy for the weekend.

Cheers,

Sean

A123: a better battery announcement

Hello Readers,

Today when I turned on my computer, I stumbled upon quite a surprise. One of the top headlines at the New York Times was all about batteries! Upon a quick search, I also found a similar article by Forbes that strips the issue down to the bare bones, no political commentary.

It turns out, the big news in an announcement by A123, which has already developed one of the first - if not only - commercially available utility scale energy storage units on the market, about a new Lithium-Ion battery technology called Nanophosphate EXT.

According to the manufacturer, the main benefit of Nanophosphate EXT will be its ability to operate in a wider temperature range with less control equipment required to maintain the batteries. While this may not sound like much, it could mean a lot for electric vehicle and renewable energy technologies.

For electric vehicles, it will mean a lighter-weight, more durable Li-ion battery. Think of a battery that allows the vehicle to go further and lasts the entire functional life of the average car today.

Click to See Source: A123 Website

Although, it is not mentioned anywhere, this breakthrough could also have a significant impact on the cost, durability, and useful temperature range of remote (non-grid) renewable energy generation systems, such as solar photovoltaic systems that rely on a battery bank. With current battery technologies, system owners need to be especially careful when choosing the size of the battery bank attached to a remote energy system.

With typical lead-acid batteries (such as those normally used in non-electric vehicles and off-grid renewable systems), the characteristics of a battery vary greatly with the temperature. As a result, battery banks typically need to be over-sized to allow for extremely cold temperatures, when batteries have a diminished capacity to store energy. Additionally, typical lead-acid batteries have a limited 'cycle life', i.e. the amount of useful energy that the battery can store quickly decreases based on the number of times the battery is fully discharged and then fully recharged.

By comparison, current Li-ion batteries have a longer cycle life than lead-acid batteries, but they also require a lot of expensive, non-energy storing, control equipment in them to ensure stability (e.g. not catching on fire) and extend the life of the battery. However, according to A123, the new Nanophosphate EXT Li-ion battery, will require less of that equipment (think less expense) to operate safely AND be able to store more energy at lower temperatures AND have a longer cycle life.

So if A123 is able to bring this technology to market, it could be a game changer not only for electronic goods like laptops, but it could also impact energy storage in pretty much every area: regular vehicles, electric vehicles, remote renewable systems, and perhaps even large utility-scale renewable projects (see: the Background section of my Dissertation).

We shall have to wait and see!

Charged-ly,

Sean

Energy Future TED Talk

Hello Readers,

This is potentially the most important and informative TED Talk you will see this decade. The speaker is the head of the Rocky Mountain Institute.

Please watch this.

Thanks,

Sean

Li-air Batteries for EV's

Hello Readers,

Today, I stumbled across an interesting article on IBM's research initiative to develop light-weight electric vehicle batteries that store charge using lithium and oxygen from the air. A short video from the article is below, and more links about energy storage are given in the article as well.

Enjoy,

Sean

Energy Storage TED Talk

Hello Readers,

If you have been following my blog, you may remember that I wrote my graduate dissertation on the GHG emissions impact of adding energy storage technology to the electric utility grid. Of course, at the time I wrote it, there were only a few energy storage technologies that were close to meeting the technological and economic thresholds that would be practical in the real world. Instead, I had to do my calculations on the premise that those thresholds could be reached.

Thus, I was ecstatic to discover a TED Talk by Donald Sadoway, a professor at MIT, about a technological breakthrough in utility-scale energy storage. Please enjoy the TED Talk below.

Cheers,

Sean

Hello Readers,

When I saw this new TED talk about literally growing batteries, I knew I had to share it. This is especially relevant to our ability to manufacture batteries and other energy storage systems (as discussed in my dissertation).

Please enjoy!

~Sean

A personal update: Utility-Scale Energy Storage

Hello Readers,

Tonight I attended a lecture hosted by 4CP about energy storage on the utility grid. If you've been following my blog, you may note the serendipitous nature of such a lecture for me. If you haven't, suffice it to say that I just got my results back from my Master's dissertation on the GHG emissions impact of incorporating energy storage on the utility grid, and I got a 'distinction'... the British way of noting 'hono(u)rs'.

I was quite pleased with the results of my dissertation; however, after sitting through a lecture by an industry professional on my dissertation topic and not learning a single thing (and in fact mentally noting a few inconsistencies with my background research), I have satisfied myself that I actually did learn something about energy storage on the utility grid while writing my dissertation.

Of course, I am using this post as an introduction to my next several posts, wherein I will post my dissertation in sections (after sending a copy to those who helped me out with the dissertation). Thus, please check back over the next several weeks if you are interested in learning what I learned about how adding energy storage to the utility grid will impact GHG emissions and subsequently anthropogenic climate change.

Till then, stay green dear readers!

~Sean

Change... in which I can (finally) believe

Hello Readers,

As you have likely heard already, White House officials recently announced plans to install solar PV and solar hot water systems on the roof of 1600 Pennsylvania Ave. This will replace the system that was removed in 1986 during the Reagan administration. You will note that the 24-year gap roughly equals the 20-25 year warranty offered on solar panels, which means that the entire lifetime of a system could have been generating power if they had not been removed.

Although, a new solar energy system on the White House seemed like a bit of greenwashing, which would not have been surprising given the relative inaction (or at least lack of concrete action) on climate change and energy independence since Obama was elected nearly 2 years ago. However, an announcement today by Ken Salazar showed some substantial change (believe it or not).

It turns out that the White House has cleared the way for a 709 MW and a 45 MW system to be built on federal lands in California (with a few thousand more MW of capacity in the pipeline for approval by the end of the year). Granted, some may consider this a stunt for the midterm election. Even so, any election year stunt that allows for over half a million homes (and possibly closer to 2 million homes) to be powered by solar power is okay by me!

The New York Times article relating to the announcement mentioned a need for additional transmission capacity to be built. However, it did not mention any plans for energy storage! After doing all of the research for my dissertation, I cannot help but wonder if anyone in the political realm has considered that option as a way to alleviate the grid congestion that will occur when these mammoth solar generators come online.

Hopefully, the utility regulators in California, which are well aware of their options based on what I saw during the PJM-EPRI conference on Energy Storage, have the sway to make a suggestion about incorporating energy storage into these plans (and/or the budget to do it themselves!).

anti-schadenfreudlich,
Sean Diamond

P.S. Later this month I should be receiving the results of my dissertation, so I will be dispersing the final version of it accordingly. Thanks for waiting so long!

A Timely Article...

Hello Dear Readers,

One week before my dissertation is due, I have found a timely article that briefly describes my dissertation topic: energy storage on the electric grid. If you have tried to read through my dissertation proposal or listened to me try to summarize my dissertation in person and had trouble understanding, I encourage you to read the brief article from the New York Times. Then, just understand that I am studying the impact of those technologies on the overall greenhouse gas emissions of the grid.

That's all for now. Wish me luck as I finish my dissertation!

Sincerely,
Sean Diamond


This post references the article:
Wind Drives Growing Use of Batteries
By MATTHEW L. WALD
Published on July 27, 2010
In the New York Times
http://www.nytimes.com/2010/07/28/business/energy-environment/28storage.html

Survey Release!

Hello Readers,

Today I am distributing the survey for my dissertation. I will be sending out the survey via email to contacts that I have already found. Also, I have posted information about my dissertation and the survey on this website. Here is a list of links you can use to find out about the survey:

• The Dissertation Proposal
  This page will help you understand a little bit about why I am doing what I am doing in my dissertation.
• The Introduction Letter
  This page is useful for potential survey participants (people and companies that work with electric utility companies and energy storage technologies).
• The Survey
  This page provides a preview of the survey and offers instructions for participating in the survey.

I greatly appreciate any assistance you may be able to provide with my dissertation. In order to complete my dissertation on time, it is imperative that I receive all survey responses by 30 June 2010. If you are not able to participate in the survey but you know others who can, please forward along links to these pages. Also, I have set up an email account specifically for my dissertation, so all correspondence can be sent to me at seandiamondsustainability@yahoo.com.

Thank you for your time and interest!

Sincerely,

Sean Diamond

Dissertation Proposal: Energy Storage

Hello Reader,

As I promised in my previous post, this post includes part of my dissertation proposal. I have decided to spare everyone the mundane details surrounding my time table and contingency plans. I hope this post gives you a good sense of the need for studying electrical energy storage.
----------------------------------------

SUMMARY

In the context of global climate change, energy consumed to generate electricity for regional electric utility grids plays a significant role. The need for a comprehensive simulation focused on optimizing greenhouse gas emissions on a contemporary, developed electric utility grid through the use of viable, large-scale energy storage is established. A methodology for developing such a simulation and a schedule for producing a study are proposed. Contingencies to potential problems are also addressed.

I.    INTRODUCTION

As developed countries seek to modernize their electric utility grid, whether for the sake of cost savings, the environment, energy security, grid stability, or some combination thereof, many utility companies have started to implement or consider the use of large-scale energy storage (ES) systems to meet present and future demand. Careful consideration of present and future grid scenarios and issues such as inefficiencies in traditional non-renewable energy generation (Dell and Rand 2001), the intermittency of renewable energy sources (Pickard et al 2009), the increased use of distributed generation technologies (Bayod-Rújula 2009), and the introduction of plug-in electric vehicles (EVs) (Verhaegh et al 2010) provide a number of opportunities to implement energy management ES systems that reduce the overall greenhouse gas (GHG) emissions of a grid thereby lessening the region’s impact on anthropogenic climate change.

II.    JUSTIFICATION

Sims et al (2007) explain that energy use currently accounts for 70 percent of global GHG emissions and of this 40 percent is used to produce electricity. Furthermore, approximately two-thirds of electricity is generated through the combustion of fossil fuels (i.e. coal, lignites, natural gas, and oil), which creates direct GHG emissions (Sims et al 2007). As a result, comprehensive attempts to mitigate anthropogenic climate change will likely involve addressing electricity generation and use in some form or another.

Due to the contemporary structure of electric grids, electricity must be generated at the time of use, which causes inefficiencies that exacerbate the associated impact on anthropogenic climate change. Even everyday conditions such as diurnal fluctuations in demand are a source of avoidable emissions (Dell and Rand 2001). The inclusion of ES systems on a grid can decouple electricity supply from demand, reducing the impact of such inefficiencies (Chen et al 2009, Dell and Rand 2001).

Chen et al (2009) indicate diurnal and annual demand fluctuations not only cause generation inefficiencies but also require that generation capacity be over-built to meet peak demand that may only last a few hours each year. With sufficient ES capacity to meet such peak-demand the construction of additional primary generation capacity can be delayed or avoided (Dell and Rand 2001).

Dell and Rand (2001) suggest that peak-shaving and load-leveling with ES can reduce the need to maintain plants in “spinning reserve” (i.e. generating electricity at sub-nominal values) to avoid a short-term shutdown. When fossil fuel plants are operating in spinning reserve, the GHG emissions per kWh of generation is greater than emissions during optimal generation (Voorspools and D’haeseleer 2000). Instead, plants can be maintained at optimal generation levels by running at a constant or near-constant rate (load-leveling or peak-shaving respectively), charging ES systems during low-demand and allowing ES systems to meet demand during peak conditions (Chen et al 2009).

In addition to the limitations of traditional energy production, ES appears to play an even greater role in future development plans and attempts to mitigate climate change. Perhaps most significantly, as developed nations look to integrate emission-free renewable energy technologies with intermittent generation into their energy portfolio (e.g. NCSC 2009), the integration of ES systems on the utility grid may be not only desirable but necessary for the practical and economic viability of large-scale implementation (e.g. Pickard et al 2009, Aguado et al 2009, Benitez et al 2008). Additionally, Voorspools et al (2000) has suggested that studies analyzing GHG emissions associated with “emission-free” technologies need to take into account indirect emission embedded in construction in addition to the direct emissions from the fuel cycle, which is traditionally the limit of the scope of energy generation analyses.

Bayod-Rújula (2009) and Verhaegh et al (2010) suggest that the future of the electricity grid in developed countries will likely involve increased distributed (non-centralized) generation and/or the wide-scale use of EVs and residential heat-pumps, which may vastly alter the nature of the contemporary diurnal supply and demand cycles. In the US in particular mass production of EVs seems imminent within the next several years (Woody and Krauss 2010). Thus, earlier studies that have not consider these developments will need to be reexamined or taken with caution.

Chen et al (2009) have thoroughly explored the state of ES technologies in the present and near-future. Their analysis roughly divides ES technologies into two categories (see TABLE J1), those that are useful for power quality management (capable of making short-term, high power, low energy interventions) and those that are useful for energy management (capable of mediating variations in supply and demand). Though power quality management ES technologies have a definite role to play to play in the future stability of the electricity grid (e.g. Shayeghi et al 2009 and Hartikainen et al 2007), their likely contributions seem difficult to quantify in an absolute manner. Therefore, it seems more reasonable and useful to focus on energy management ES and the tangible effects it could have on GHG emissions in the near-term. Of course, focusing on the near-term means that some technologies are not yet viable on a commercial (large-) scale (Chen et al 2009). In fact without even considering cost limitations, only pumped-hydro power, compressed-air, and certain types of batteries and flow-batteries have examples of successfully developed MW-scale systems capable of operating for multiple hours.

Voorspools and D’haeseleer (2000) stress the need for a simulation tool, stating: “Since it would be impractical to constantly monitor the instantaneous composition of the power system and to calculate (or measure) the corresponding emissions… [f]or studies or scenarios carried out for future or hypothetical developments, monitoring is not even an option and, hence, a simulation tool is essential.” They also highlight the need for “instantaneous” rather than “linear” emission approximations (i.e. not using daily or annual average figures) to accurately determine GHG emissions under varying demand-supply scenarios (Voorspools and D’haeseleer 2000). Despite the need for a sufficiently resolved time-scale, the duration need not be exceptionally long. For example, Verhaegh et al (2010) elected to focus on one week periods during different seasons (e.g. winter and summer), which suggests that this is a reasonable approach to avoid simulating an entire year’s worth of data.

Finally, while a number of energy simulation studies have examined some combination of traditional generation, intermittent generation, and ES systems, the majority of recent studies appear to have optimized their results for financial gain (e.g. Aguado et al 2009, Benitez et al 2008, and Crampes and Moreaux 2010); however, optimizing a system for financial gain will likely result in inefficiencies with regard to GHG emissions (Voorspools and D’haeseleer 2000). Thus, with the issue of global climate change in mind, there is a distinct need to consider situations optimized to reduce GHG emissions.

III.    OBJECTIVE

The objective of this study is to assess the potential near-term impact on greenhouse gas emissions of a large-scale implementation of energy storage systems on an electric utility grid in a region with a fully developed grid system. To achieve this objective, technical data will be collected and a simulation will be developed.

<---sections omitted here--->

VII.    OUTCOME

This study should fill a significant gap in the literature by combining ES with a variety plausible demand and supply scenarios and focusing on GHG emissions optimization rather than pure fiscal optimization. The final results of this study should offer insight regarding the degree to which the addition of energy storage on an already-developed, though evolving electricity grid can enable GHG emissions reductions. These results should be particularly valuable as utility companies and regulators evaluate their options to meet and develop current and near-term energy portfolio standards.

For a list of references please see the accompanying post.

Wind Turbine Intermittency

Hello Reader,

I wanted to draw your attention to a New York Times article from the past week that highlights one of the major challenges facing developed countries as we try to connect increasing numbers of wind turbines to national and regional electricity grids. That is: intermittency.

Wind turbines are notorious for generating intermittent energy. From a physical perspective this makes sense, because wind does not blow at the same speed all the time. However, when it comes to the electricity grid intermittency can be a huge issue.

On a very small scale, such as a single isolated wind turbine on a farm, this issue can be over come by simply combining the wind turbine with a battery storage system. In such cases, intermittency is not really an issue unless the wind simply stops blowing for days at a time.

On a somewhat larger scale, such as the current state of the US electricity grid, where wind turbines only make up a small percentage of electricity generation the fluctuations are manageable. That is the gaps in generation caused by wind turbine intermittency can be filled in by other generation sources.

Of course, as the article indicates when wind energy starts to make up larger percentages (e.g. 20%) of generation sources, intermittency can pose serious risks to grid stability (e.g. increasing the risk of brownouts and blackouts). The article suggests studies are testing the possibility of connecting multiple turbine farms together to level off the effects of intermittency and provide a more consistent power source. From a physical perspective this also makes sense because when the wind is blowing in one location it may not be blowing in another and vice versa. This means electricity generation will be averaged out.

While this does appear to be a crucial step towards large scale implementation of wind energy, more infrastructural concerns must be addressed. One such step includes the mass introduction of electrical energy storage, which allows electricity to be produced at one point in time (e.g. when the wind is blowing hardest) and used at another point in time (e.g. when you wake up and turn on your electric razor). Unfortunately, the current structure of the electricity grid is not compatible with this concept. As it stands, electricity must be produced as it is being used and at no other time.

Not only is this an issue for installing wind turbines, but it also has massive impacts on the efficiency of traditional fossil fuel and nuclear plants as well. As such, energy storage is the topic of my postgraduate dissertation. Next week I will post part of my dissertation proposal, which explains more about the issue and the need for research into the field. In the meantime, I encourage you to look into the topic for yourself.

The article I referenced within this post is:
A Grid of Wind Turbines to Pick Up the Slack
By HENRY FOUNTAIN
Published: April 12, 2010
http://www.nytimes.com/2010/04/13/science/13obwind.html

Sincerely,

Sean Diamond