Down by the Water* - Hydro Power in New Hampshire – Part 1

My office is in Manchester, in Franklin Pierce University’s graduate school which is located in one of the renovated mill buildings located on the Merrimack River. From the conference room there is a great view of the river and the upstream Amoskeag dam. This is a 30-foot high, 710-foot long concrete dam that holds back the Merrimack River at this point so that the water can be directed through the turbines at the Amoskeag Power House located on the western bank of the Merrimack.  These turbines have a combined generating capacity of 16 MW. The photos below show my view of the dam wall and a Google Map satellite image for an overhead view. This dam was originally commissioned in 1924 to service the Manchester mills. While gazing at the river this week during a meeting, I decided it was time to turn my attention to the topic of hydro power in New Hampshire. This post is the first in a multi-part series on this topic.

Man has utilized the power of water (hydro power) for centuries. In the late 1700s and into the 1800s, advances in technology, powered by running water (and eventually by steam) is what lead to the industrial revolution. Throughout New England, textile mills were established along the main rivers, most notably the Blackstone River that runs down through Worchester, Massachusetts into Rhode Island and the Merrimack River that follows a route through New Hampshire into Massachusetts. The river flow turned water wheels and turbines which, through a system of gears, shafts, and belts, were used to drive machinery inside the mills.

In the 1880s, water-driven turbines were combined with electric generators to generate the first hydroelectricity, and in 1882 the world's first hydroelectric power plant started operation on the Fox River in Appleton, Wisconsin. From that point on, the use of hydroelectricity grew phenomenally and, in 1940, hydro generated 40% of all electricity in the US. Since then, demand for electricity has increased ten-fold, but natural gas-, coal-, and nuclear-fired operations were established to fill the need. Hydro power output grew, but its share of electricity production has dropped off to about 6 to 8% of the electricity generated in the US today.

Hydro operations range in size from the very large 6809 MW Grand Coulee Dam in Washington state, the 2515 MW of the Robert Moses Niagara Power Plant and the 2080 MW of the Hoover dam on the Colorado River to “hobby” projects less than 1 kW in capacity. (Remember there are 1000 kW in a MW.) There are about 1750 hydropower operations in the US: most of them are much smaller than in size than the very large Hoover Dam operation which we usually associate with hydropower.  In fact, most hydroelectric operations in the US are much smaller - almost 90%  are less than 30 MW in size.

Hoover Dam Hydroelectric Plan

All hydropower operations, whether private, municipal, or state-owned, are licensed by the Federal Energy Electricity Commission  (FERC) – the  federal “godfather” of the electricity business. There are 41 FERC-licensed hydro operations in NH, ranging in size from 136 MW to 58 kW.  Small projects, such as those less than 10 MW installed on an existing dam or those of less than 40 MW installed on a waterway used for another purpose (such as an irrigation canal), are exempt from FERC licensing. There are 43 such exempt facilities in NH, ranging from the 3.5 MW Gregg’s Falls operation on the Piscataquog River in Goffstown to a 5 kW operation on Marden Brook. FERC licenses often involve combinations of hydro operations run by a single operator on a stretch of water:  for example, the three PSNH operations on the Merrimack River are combined into one license. I also noted that the very large Moore and Commerford hydro plants on the Connecticut River are listed by FERC as Vermont operations. These licensing/classification artifacts can cause confusion, especially when data on generation, as provided by the Energy Information Agency (EIA) and used later in this post, is reviewed.

There are many different ways of classifying hydro operations. The first is by size. Large hydro plants in the US are generally considered to be those above 25 MW in capacity but international standards consider those above 10 MW to be large. Most of the hydro plants in New Hampshire are small operations: within this class there are subclasses which typically have the following size ranges:

·                                Mini                <1 MW

·                                Micro              <100 kW

·                                Pico                <10 kW

·                                Family             <1 kW

To give you a sense of what these capacities mean, it is important to remind ourselves of the difference between power and energy.  I discussed this topic in the I’ve Got the Power! blog a while ago. As a reminder, remember that electrical energy is the ability of an electric current to do work − such as producing motion, heat, or light. The units of electrical energy are kilowatt hours (kWh) or megawatt hours (MWh). There are 1000 kWh in one MWh. Electrical power, on the other hand, measured in kilowatts (kW) or megawatts (MW), is a capacity, i.e., the rate at which energy can be produced from a generator. Large generators, which can produce more energy per unit of time, naturally have larger capacity or power ratings.

The confusion between power and energy often stems from the similarity of the units: kilowatt hours or megawatt hours are energy units, and kilowatts or megawatts are power units. However, it is important to understand that even though the units seem similar, there is a world of difference between them. This difference stems from the simple mathematical relationship between energy and power;

Energy = Power x time.

I find it is always useful to understand these relationships from a homeowner’s point of view. Consider that an average US household uses 11,000 kWh per year of electricity (~900 kWh per month). If you had to generate that electricity yourself and you were going to do it over 24 hours a day for 365 days per year, you would need generator with a power rating of 1.3 kW.

The calculation would be done as follows:

Energy = Power x time

Power = Energy / time

Power = 11,000 kWh/(365 days x 24 hours/day) = 1.3 kW.

Of course, this calculation is based on a daily average, but our daily electricity use is actually rather “lumpy”:  there is a first peak in the morning as we turn on the lights, make coffee, heat up the house, and take hot showers, followed by a second and larger peak in the late afternoon/evening when we are making dinner, watching TV, doing the laundry, turning on the electric blanket, reading this blog, etc. If you were to actually buy a generator, you would want a unit that has a capacity of more than the average 1.3 kW so that it could handle the peaks in usage. This is why backup generators for homes often have sizes of the order of 5 kW to 15 kW. But I digress somewhat (I may come back to the topic of home generators in a future post)….

The second classification of hydro plants is by type of operation. The three main types are:

• Reservoir or Pond-and-Release Operations: We most commonly associate these with hydropower and they involve large concrete dams holding back enormous reservoirs of water with the power plant at the base, as shown in the Hoover Dam picture above. The reservoir provides for a great deal of storage and steady power generation even during the dry season. These operations usually involve the upstream flooding of large tracts of land and significantly impact downstream water flows. The water level in the reservoir can also fluctuate greatly, depending on the incoming water flows and the discharges through the power station.
• Run-of-River Operations: These hydroelectric plants depend on the natural drop in the river elevation. A portion of the upstream river flow is sometimes diverted through a large pipe (called a penstock) to a downstream generator plant, after which the water flow is reintroduced into the river (see the figure below). These operations often have dams at the upstream location to provide the water diversion point but their storage capacity, called pondage, is limited and, as such, these operations are more subject to the vagaries of seasonal precipitation and natural river flows. With limited storage, the reservoir level tends to remain fairly constant – excess river flow simply spills over the top of the dam. Electricity production can therefore vary substantially over time. Because these operations don’t involve large amounts of storage or flooding of large acreages of land, they tend to viewed as more environmentally friendly or “greener” than the larger reservoir operations.
• Pumped Storage: These operations involve pumping water from a river uphill to a reservoir at a higher elevation during low electricity demand and low cost periods. When electricity demand increases and prices are high, these operations then run in reverse and the water in the reservoir is drained through a turbine back into the river, generating electricity in the process. There are a three of these operations in New England with a combined capacity of 1696 MW.

Source: IPCC

In NH, we do not have any pumped storage operations but we have reservoir and run-of-river operations.  Data from the EIA indicates that there are 92 hydro generators in NH with a combined name-plate capacity of 446 MW and a total winter capacity of 511 MW. The ten largest NH hydroelectric operations are listed below.  The Moore and Comerford dams, located on the Connecticut River which runs between New Hampshire and Vermont, are the largest hydro operations in all of New England. All operations listed are individual dams, except for the Great Lake Hydro-owned operation on the Androscoggin River in the Berlin area which is a series of different dams and 21 generating facilities. The largest PSNH-owned operation in NH (and the one that distracts me during meetings)  is the Amoskeag dam on the Merrimack River.

Source: EIA

As a wrap-up for this post, I thought a comparison with other New England states would be interesting. The table below lists total electricity production capacity (the power of the generator) and hydro capacity by state for 2012, as well as total production of electricity and hydroelectricity. The data include conventional hydro only and excludes pumped storage operations. We can see that Maine is the “hydro powerhouse” of the New England region, with the largest capacity, followed by NH. The upper New England states, New Hampshire, Vermont, and Maine  provide the bulk of the region’s hydro generation capacity.

I note with interest that, even though Maine total hydro capacity was only 17% of its total generating capacity, 26% of their electricity output for 2012 was generated from hydro. This means that their hydro plants worked very hard in 2012, which is indicated by the highest capacity factor for their combined hydro plants. (Recall from I’ve Got the Power! that capacity factor is the ratio, expressed as a percentage, of the actual electricity output from a generator over a year compared to the theoretical output if the unit operated 24 hours/day 365 days per year.) The comparative numbers for NH are quite different. In orange I have highlighted that hydro represented 10% of NH generating capacity but, in 2012, it was, surprisingly, only responsible for 7% of the NH total electricity output. The capacity factor of all NH’s hydro plants, in yellow, was therefore an extraordinary low 33%.

Source: EIA

This anomaly is quite striking and some follow-up research is warranted. It is clear that hydro power is intriguing topic and I plan to continue my explorations in future posts. Now, when I gaze out the windows at the Merrimack River and the upstream Amoskeag dam during faculty meetings, my colleagues can be assured that my distraction is not idle daydreaming; instead I will be thinking of river flows, generating plants, and capacity factors!

Until next time, remember to turn off the lights when you leave the room.

Mike Mooiman

Franklin Pierce University

mooimanm@franklinpierce.edu


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(*Down by the Water – A great tune by one of my favorite indie groups, The Decemberists. These guys are great song writers and I always look forward to their new releases. Here they are from Austin City Limits – the best music show on TV. Enjoy Down by the Water.)

I’ve Got the Power!* – Electricity Production in New Hampshire

My post this week is part informative and part instructional. When we debate and discuss energy issues, a couple of key concepts come up time after time and to be a contributor to an energy discussion, we have to know, or familiarize ourselves with, some technology and terminology. This week I want to explain two fundamental energy concepts. The first is the difference between energy and power, and the second is capacity factor. I will then show how they can be applied to electricity production in New Hampshire.  

Let's start with the difference between energy and power. The terms energy and power are often used interchangeably. This is OK in a general conversation, but in an energy related discussion it can lead to confusion, misunderstanding and bad decisions. It is essential to be specific about which term you are discussing so let's take a crack at distinguishing between the two.

 

The standard scientific definition is that Energy is the ability of a system to do work. It is a quantity which we need to get something to move, heat up, light up, burn, explode, etc. Energy also comes in different forms, for example, electrical energy, chemical energy, nuclear energy, kinetic energy etc. and much of energy technology is about converting one form of energy to another in the most efficient manner. Some of the more common units of measurement for energy are kilowatt hours (kWh), megawatt hours (MWh), BTUs, among others.

 

Power, on the other hand, is the rate at which energy is produced from a fuel source or is converted from one energy source to another. Units of measure for power include kilowatts (kW), megawatts (MW), BTU/hour or horsepower.

 

The confusion between these two often stems from the similarity of the units like kilowatt hours, which is an energy unit, and kilowatts, which is a power unit. However, it is necessary to understand that even though the units seem similar, there is a world of difference between them. This difference stems from the simple mathematical relationship between energy and power;

 

Energy = Power x time.

 

One my students in the Energy and Sustainability program at Franklin Pierce University recently noted that energy and power are analogous to distance and speed. Energy, like distance, is a quantity, whereas power is a rate like speed. Like the relationship between energy and power, the relation between distance and speed is written as;

 

Distance = Speed x time.

 

Let's consider a simple backup generator that I have been eyeing at Lowe's – the Generac 5500 Watt Portable Generator.

 

  (Picture source: Lowes)

 

This unit is rated at 5500 Watts or 5.5 kilowatts (kW), so the power of the unit is 5.5 kilowatts. If I were to run this unit for 1 hour, I would produce,

 

5.5kilowatts (kW) x 1 hour = 5.5 kilowatt hours (kWh)

 

of electrical energy that I could use to run my home. Running it for 24 hours would produce 5.5 kW x 24h = 132 kWh of electrical energy. The power rating of 5.5 kW is a measure of the rate at which the backup generator can take the chemical energy in the gasoline and convert it to electrical energy that I can use to keep my home running during a blackout. The larger the motor on the generator, i.e., the greater the power, the faster is the rate of energy conversion. In automobiles we are looking to convert the chemical energy in gasoline into forward kinetic motion to get us from point A to B. Again, the greater the power of the engine, the faster will be the rate of energy conversion. The pictures below illustrate this point.

 

(Picture source: Maserati)

 

The Maserati with its higher power, and larger, 700HP motor has the ability to more rapidly convert the energy in the gasoline tank into forward kinetic motion than my trusty and somewhat dusty blue Prius with its 80 HP motor. These two automobile engines, under specific circumstances, can produce the same amount of energy, however, the Maserati can do so in substantially less time. The Maserati will do so a lot less efficiently than the Prius but with a whole lot more fun. Even if I can't barrel down the highway at very high speeds, at least I will have my energy efficiency smugness to compensate me for the lack of admiring or envious glances for my ride. We will come back to the topic of energy conversion efficiency in a future blog post.

 

Let's go back to the Generac 5500 generator unit so we can discuss the second fundamental concept for this post – capacity factor. If I could run the generator solidly for 24 hours a day the whole year, I theoretically could produce;

 

5.5kW x 24h/day x 365 day/year = 48,180 kW of electrical energy.

 

However, if I were to use the generator only for 1 week during the year, say during a blackout, I would produce;

 

5.5kW x 24 h/day x 7 days = 924 kWh of electrical energy.

 

Dividing actual produced energy by the maximum that theoretically could have been generated in a 24/365 scenario produces a ratio called the capacity factor. In my case, it produces a figure of 0.019 which converts to a percentage of 1.9% and that would be the capacity factor of my generator for that year. In other words, my generator only ran at 1.9% of its maximum potential output. The capacity factor is a useful measure of how much of the capacity of an energy generating device was utilized over a time period, typically one year.

 

With these basic terms, energy, power and capacity factor under our belts, let's turn back to New Hampshire energy issues and particularly electricity generation. I have examined the 2011 electricity generation figures for New Hampshire that were published by the Energy Information Agency (EIA) and have combined, in one table, the number of generating units, their combined power, the energy produced from these units and the overall calculated capacity factors.

 

  

In 2011, there were 149 energy generating units in New Hampshire ranging from the large nuclear power at Seabrook, four coal fired plants, the wind farm in Lempster and 93 small hydroelectric operations, among others. The combined nameplate capacity of the generating units was 4,490 Megawatts or 4.5 Gigawatts, and they generated just over 20 million megawatts of electrical energy in 2011.

 

On examining the capacity factors, it is interesting to note how far they are from 100%. The only way a generating device can run at a capacity factor of 100% is by running 24 hours 365 days a year which is simply not practical or realistic. Equipment breaks down and has to be repaired or has to be shut down for maintenance. Moreover, power plants generating electricity make operating choices, based on prevailing wholesale electricity prices, fuel prices as well as demand to throttle back their units from their name plate capability. This reduces the amount of electricity produced which, in turn, reduces the capacity factor.

 

The units with the highest capacity factors are nuclear and wood fired operations which operated with capacity factors of 76% and 70%, respectively. These operations supply a great deal of the base load power to the electrical grid and therefore tend to run all the time except for maintenance shutdowns and reduced output during periods of low demand such as late evening and early morning hours.

 

Coal and natural gas ran at about 50% of their capacity and wind energy, which is very much dependent on wind speed and availability, has a capacity factor of 0.31 which is typical for wind projects. Oil and diesel based generators only have a capacity factor of 0.017 or 1.7%, which indicates these units are seldom used, due to the cost of producing electricity from oil. They function as back-up generators and are only used in an emergency. In many respects they are just like the small Generac 5500 unit, my present object of desire.

 

Even though the 149 New Hampshire based generating units are run by different operators with different technical and economic considerations, it is useful to consider their aggregated capacity. As noted above, the combined nameplate capacity of the generating units is 4,490 Megawatts or 4.5 Gigawatts. This combined capacity in a single unit would be one mammoth sized generator - we could call it the "New Hampshire Megarac 4500" – which is almost a million times larger than that unit I have my eyes on at Lowe's. 

 

 

 

(Generator Picture source: Lowes)

Based on 2011 data, this NH Megarac 4500 was operated at a capacity factor 0.51 which means the combined NH generating facilities only generated 51% of the energy that was theoretically possible. So, if we lose some of generating units in state, we have some excess capacity. However, we need to keep in mind that practical considerations such as cost and availability of fuel and maintenance requirements need to be taken into account when we shutdown generating units and expect others to operate at higher capacity factors. We also need to keep in mind that New Hampshire electricity generation is not an island unto itself. We feed into and draw electricity from the ISO-New England bulk power generation and transmission system which coordinates electricity supply and demand throughout New England. The six New England states have a combined capacity of about 35,000 MW of electrical capacity from 860 generating units.

 

Hopefully this has been an informative and instructional post and you now know the difference between energy and power and you have an appreciation for capacity factors. As you can see, we have a lot a capacity for generation in New Hampshire but it is crucial to appreciate that not all this capacity can be tapped at any one time. Running these generators depends on complex number of issues which include demand, cost of and availability of fuel, maintenance shutdowns and financial considerations and it all functions remarkably well most of the time due to the coordination of supply and demand that happens in the ISO-New England grid system.

 

In the meantime, if you see me in the parking lot at Lowe's trying to load a Generac 5500 into my dusty blue Prius, stop and give me a hand. Until next time, remember to turn off those lights when you leave the room.

Mike Mooiman
Franklin Pierce University   
mooimanm@franklinpierce.edu
3/18/13

 
(*The title of this week's blog comes from 1990's tune by Snap!, a German rap/pop group. Their song "The Power", features an incessant "I've Got the Power!" refrain. You do know the song, but as soon as I thought of it, the refrain became a relentless mind worm burrowing its way into my brain and I have not been able to get rid of it. Annoyingly, I now mentally hear it every time I flip a light switch. Here is the Youtube clip but be forewarned about that mind worm.)

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