Energy Currency

One surprisingly difficult thing to learn when studying energy is all the different measurement units that can be  – and are – frequently applied.

Just as one Euro can be converted to about 1.3 U.S. dollars, energy units can also be freely converted.  For instance, one kilowatt-hour is equivalent to 3,412 British Thermal Units (Btu) of energy.  Some of the more common measurement units of energy are listed below:

  • Joules
  • British Thermal Units (Btu)
  • Watt-Hours
  • Kilowatt-hours (kWh)
  • calories
  • Calories (this is 1,000 small-c calories, and what we refer to in food energy content)
  • Horsepower-hours
  • Quads
  • Ton-Hours (Tons are units of heat, not just weight.)

All of these units can be converted to the others.  Horsepower-hours can be converted to Calories, for instance, or kWh.

At some point I will double back and explain what some of these units mean.  For example, 1 calorie is the energy needed to raise the temperature of 1 gram of water by 1 degree Centigrade.

Energy and Power are intimately linked, but are quite different.   Energy is equal to power multiplied by time.  The fact that Watt-Hours is a unit of energy suggests, correctly, that Watt is a unit of power.  Power retains its colloquial meaning of intensity, generally speaking.  So, for instance, a stereo system with a 100 Watt output can play louder than a 50 Watt counterpart.  Some of the more common measurement units of power are listed below:

  • Joules per Second
  • British Thermal Units per Hour (Btuh)
  • Watts
  • Kilowatts
  • Horsepower
  • calories or Calories per Hour
  • Tons (thermal tons, not weight)

Here too, the units are readily converted one to another.  For example, tons of cooling can be readily converted to Btuh.

Aside from not confusing power and energy terms, the fledgling student of energy must also contend with some rather perverse naming practices.  Consider for instance, that kWh and Btu both refer to energy, while kW and Btuh refer to power.  That “h” jumping around can be surprisingly confusing when you are also trying to master the concepts of energy and energy conservation.

So be careful out there…

I’m probably wrong

I hope I’m wrong.

But I have this sneaking suspicion that some of the people who question climate change partially base this on a belief that burning fossil fuel does not necessarily add carbon dioxide to the atmosphere.  That this is somehow speculative or a matter of debate.

There is no debate on this matter.

Coal, oil and natural gas liberate heat when the carbon in their composition combines with free oxygen in the air to produce CO2.  There is no way around this fact. (Okay, it’s true that the combusted hydrogen in hydrocarbons also liberates heat, but we aren’t going to worry about that for our present purposes since the combustion byproduct of hydrogen is just water vapor.)

So, while you may not believe that rising carbon dioxide levels contribute to climate change, and while you may even be treated with deference when expressing this opinion, to assert that mankind is not contributing to the elevated CO2 levels seen in the atmosphere is a preposterous claim that denies fundamental facts about combustion.

We’re putting CO2 up there in the atmosphere without question.

A couple of interesting facts.

The atomic weight of carbon is 12.  The atomic weight of oxygen is 16. (you may be asking, 12 and 16 what? ounces? pounds?  butterfly wings?  Turns out it doesn’t matter for our purposes, as I will show…)

What that means is that when fuel is burned and converts from carbon to carbon-dioxide, the weight of the carbon dioxide is almost 4 times heavier than the carbon that was burned.  Why?  Look at the atomic weight ratios

Carbon (12) + 2 Oxygen (16+16) ==> Carbon Dioxide (12+16+16)

Ratio of CO2 weight divided by the weight of the burned carbon is 44/12 = 3.7

What this means is that a ton of coal (which is mostly carbon) will result in about 3.7 tons of carbon dioxide emissions when burned.  This is not a theory.  This is not just possible.  This is non-negotiable.

You may be wondering about the hydrogen in fuels such as natural gas or petroleum. If you look at natural gas, the chemical composition is mostly CH4.  The combustion equation is pretty simple:

CH4 + 2O2 ==> CO2 + 2H2O + liberated heat (about 22,000 Btu per pound of natural gas)

Note that the H2O combustion product is just  water vapor, which is benign.  This makes pure hydrogen a very attractive fuel, at least in theory.

Also note that when we discuss fuels, we are discussing something different from energy or power.  Fuels are repositories of stored energy, and the rate at which we burn fuels determines how much power is generated.  Some common combustion fuels include:

  • Fuel Oil
  • Coal
  • Natural Gas
  • Petroleum
  • Peat
  • Wood

Note that the energy content of fuels is pretty well defined.  For instance, coal might house 25 million Btu of energy per ton, depending on the coal type.   Somewhere along the line I will provide more detailed fuel energy content data and show how the combustion calculation are performed.

Right now I’m just getting some preliminary stuff out of the way as I try to figure out if this blog is going to have any value to me, let alone anyone else.

So what’s wrong with Portfolio Manager (PM)?

As I mentioned in the prior post, the City of Boston is proposing that Boston facilities begin to report their energy use and carbon emissions via a tool created by the Feds called the Energy Star Portfolio Manager (PM).

PM is a web-based tool into which one enters utility consumption and cost data.  PM then performs a couple of calculations:

  1. By looking at your location, the program determines the likely carbon emissions associated with your energy use.  For example, there is far less coal-generated power on the East Coast than there is in the Midwest, so the CO2 emissions per kilowatt-hour are corresponding lower thanks to our nuclear, gas-fired and hydro sources.
  2. By dividing your energy use by your square footage, the program determines an energy density.  By comparing the energy density of similar building types (e.g. office building) one can rank them.  And if one ranks high enough, one earns the “coveted” Energy Star rating.

First, some disclosure.  The full PM program may do waaaay more than mentioned above.  I am focusing on what I understand the City to be looking to do with it in this post.

Now, this is the starting point for all sorts of commentary, so bear with me as I jump about explaining the awfulness of this tool.

You will note, first of all, that PM is performing calculations that are so simple that one sort of questions why it’s even put up on the web.  Once I know the CO2 emissions per kilowatt-hour (kWh)  and per thousand pounds of steam (MLb) in my area, why can’t I just multiply my use by said factors and divide by my square footage?

Similarly, the energy content per kWh and per MLb is well known, so PM is not needed for this, either.

Now, that might sound petulant.  If PM does the job, even if it’s simple, then what’s the problem, right? But the fact is that PM is very cumbersome and time consuming to work with, whereas doing the same calculations in a local spreadsheet (or even better, a database!) is quicker and allows for much more flexible reporting.  So there’s that.  There’s also the fact that, while you can force me to put information into PM, there is no way you could force me to use it to monitor energy performance.  So it’s simply wasted time and effort in a world that increasingly values efficiency and performance.

My second beef with PM is its lack of detail.  PM does not care about the peak demand of a building.  Nor does it care whether you use energy during “on peak” times or “off peak” times.  Why does this matter?  Well, as usual, a thought experiment can illuminate things quite readily.

Imagine two identically sized manufacturing facilities that consume the same amount of energy each year.  Well, according to what I describe above, they will grade out with identical Portfolio Manager scores.  However, it is quite possible that one facility has implemented energy savings strategies that have dropped the peak building demand, and that they are operating for more hours (and manufacturing more product) without using more total energy.

So wait a minute.

One manufacturer is creating more product while using the same amount of energy, but it’s Energy Star rating is identical to its less efficient neighbor?  How can that be?

Simple.  The program is too unsophisticated to detect operational efficiency.

Let me say that again:

The program is too unsophisticated to detect operational efficiency.

Yes, ladies and gentlemen.  The Ordinance proposed by the City of Boston will use a measuring tool that literally cannot discern the difference between an efficiently run facility and an inefficiently run facility.

This is the stuff that drives you crazy…

I should really play with PM a bit to truly stress test it.  If/when I do so, I will report back.

I may come back and add to my awfulness list.  Let’s see how time permits.

What the hell, let’s start with a rant…

It all begins here:

http://m.cityofboston.gov/news/Default.aspx?id=5997

***

So, the City of Boston has decided to announce a proposed “Building Energy Reporting and Disclosure Ordinance”.  Well.  This certainly sounds like a great idea.  Here’s a bit of the language:

“As a component of the City’s climate action plan to meet Mayor Menino’s greenhouse gas reduction goals, this ordinance would require all large and medium sized-buildings to report their annual energy and water use to the City of Boston. The proposed ordinance is intended to encourage building owners to participate in local utility energy efficiency programs and educate tenants on building performance.”

 “In order for Boston to continue to be a sustainability leader, our buildings must aggressively invest in energy efficiency,” Mayor Menino said.  “Bostonians demand buildings with high performance and this ordinance will encourage building owners to meet that demand.”

 “Major cities across the country have already adopted similar ordinances including New York City, Washington, D.C., San Francisco, Seattle and Minneapolis. Lessons learned from these cities have informed the Ordinance proposed by Mayor Menino which would require all large and medium sized buildings to report annual energy use, water use, and greenhouse gas emissions tracked through Energy Star Portfolio Manager to the City of Boston Environment Department. The City would then make energy and water use per square foot, Energy Star ratings, greenhouse gas emissions, and other identifying and contextual information for individual buildings available online.”

I mean, this sounds good, right?  What’s not to like?

Well, where do I begin?

First of all, as someone who has aggressively pursued energy conservation (and concomitant CO2 emission reductions) for well over a decade, I sort of resent the implicit message that the geniuses in City Hall (and probably the Kennedy School and other temples of wisdom not normally haunted by working-stiff engineers who actually make things work in the real world) suddenly conjured up this great idea that has seemingly eluded building managers and engineers for the past twenty years.

Secondly, the tool being used – the Energy Star Portfolio Manager (PM) – is an almost embarrassingly unsophisticated tool for evaluating energy performance in non-trivial facilities.  While we can discuss what this means later, the fact that this tool does not even bother tracking building energy demand, on-peak versus off-peak energy use, load factor or power factor speaks to the lack of thought that went into the selection of this platform.  Believe me, I have opinions about PM.

Thirdly, this ordinance is going to actively penalize those facilities, such as mine, that have saved millions and millions of kilowatt-hours and pounds of steam and ton-hours of cooling over the past decade.  I get no credit for all that work, while the schlub who’s done nothing can start doing easy stuff and look like an all star?  Really?  Do they have any idea how much more expensive it is to save energy after you’ve done dozens and dozens of projects already?  In a word, “No.”

Lastly (at least for now) this ordinance will require that we spend already scarce resources redundantly entering data into a tool of virtually no practical use in managing energy consumption, while our own sophisticated tools (in my case, a fully programmed, customized database) is shunted aside.

Let’s face it, at the core of this rant is resentment at the fact that a bunch of whiz-kids decided they came up with this great new idea, they were too important to talk with the poor stiffs who actually have to work with the building equipment and systems and know what it takes to actually implement and track energy savings or see what’s already been accomplished, and they clearly – based on the tracking tool they chose – completely don’t appreciate the complexity of the task.  Gee guys, really?  We should save energy?

All that said, the goals of making Boston more energy efficient and of reducing our carbon dioxide emissions are admirable.  But it really hurts to see such a worthwhile goal mapped out with a methodology that is so unsophisticated, and that could have been so much more promising had the city deigned to speak with the stakeholders before shoving this down 0ur throats

Of course, I’m also old enough to realize that that’s simply how the world works sometimes…