research

Awesome Energy Model Map of NYC

Feb 7, 2012

Total Annual Building Energy Consumption for New York City

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Check out this map that shows a near building level energy analysis of New York City. The map also estimates the heating, cooling, electricity and hot water use of each block.

The map represents the total annual building energy consumption at the block level (zoom levels 11-15) and at the taxlot level (zoom levels 16-18) for New York City, and is expressed in kilowatt hours (k Wh) per square meter of land area. The data comes from a mathematical model based on statistics, not private information from utilities, to estimate the annual energy consumption values of buildings throughout the five boroughs. To see the break down of the type of energy being used, for which purpose and in what quantity, hover over or click on a block or taxlot. 

 

Data Source: Spatial distribution of urban building energy consumption by end use
B. Howard, L. Parshall, J. Thompson, S. Hammer, J. Dickinson, V. Modi

Counter-Intuitive Wall Insulation Energy Study

Oct 7, 2011

A while ago, energy-models.com published a blog, "Is insulation the best energy saver?" and illustrated the number of hours where high R-values may increase energy. People may argue, "that's what an economizer is for!"  In my opinion, that of course is a good argument, but I have talked to too many people who have asked, "Why does my energy go up with increased wall insulation?"

To test this scenario, we looked to our good friend eQUEST. We built a simple building and tested it over a range of climate zones, and a range of R-values. In order to "normalize" the data, we compared everything to R-9 insulation (which is a pretty low R-value). We also made a number of assumptions:

  • L shaped Office building (100,000 sq ft)
  • Only Wall insulation was evaluated
  • DB economizer set to 65 degrees F
  • 43 percent glass (glass stayed constant at triple low-E to minimize effect of glass)
  • Medium high internal loads (1.5 w/sq ft lights, 2 w/sq ft plug loads)
  • 12 hour occupancy per day, 7 days a week
  • 76/70 F cooling/heating setpoints (82/64 unnoccupied)
  • No change in infiltration was considered
  • Different building orientations were evaluated without change to normalized results
  • 10 cents/kw-hr and 1.00/therm were used with no demand charges
  • Only climate zones A were evaluated, though results should be similar for B
The results were very surprising given that insulation only showed an increase in savings for the extreme climates: climate zones 1, 6, 7 and 8. 
For climate zones 3A and 4A, more insulation actually yielded AN INCREASE in cost (even with the economizer). Most interestingly, for climate zone 4, an obvious "sweet spot" was displayed.


Check out the results for yourself: 


Google Visualization API Sample

Miami, FL1A
Orlando, FL2A
Dallas, TX3A
Lexington, KY4A
Chicago, IL5A
Fargo, ND7A
It should be noted that a number of other locations were tested at each climate zone and the results were surprisingly consistent. The final data comes from the listed cities.

The Real Effect of Lighting on Energy and LEED points

Aug 16, 2011

EAc1 LEED points can't fall entirely on the back of the MEP!

I've probably seen as many LEED files as most LEED reviewers. What blows my mind is that most of the files I have seen save very little in lighting, even though lighting is often 25% of the building energy costs. In my opinion, this is a result of Architects and firms who, let's face it, are too set in their ways to change their designs. (Either that, or it's just plain laziness).  Perhaps, I am being harsh and they simply don’t understand the huge impact lighting has on LEED points. So, I’m going to spell it out mathematically, but first let’s see how a typical conversation goes:

"We have a design that is going to save 30% on energy costs annually. The HVAC has an improvement of 35% over the 90.1-2007 baseline, and we are using such and such.."

…..But then, I look at the lighting and see that it is designed at 1.2 watts/sq ft compared to a baseline building at 1.3 w/sq ft .

Now if you're asking, "what's wrong with this?"-  I want to ask you, "What's wrong with you and why are you reading my blog?" Okay, maybe I'm being harsh again but it's really simple math and I shouldn't need to explain it in depth. The truth is that lights are one of the best ways to earn LEED points.

Here's a rule of thumb for LEED buildings:

 Whatever your intended net savings on LEED is, your lighting design should save that percentage against the whole building method. (for buildings where lights are the typical 15-25% of savings)

Example:  

Target savings: 30%

Whole building method lighting: 1.2 w/sq ft

Designed lighting (after 10% credit for sensors) equal or less than: 1.2 *.7  = .84 w/sq ft 

Now, I see a lot of jaws drop at this, but that's only because they have been designing buildings the same way for 30 years. The message from LEED is that things need to change. The work that will go into this design will save days and maybe weeks of backtracking in the design when you find that it’s mathematically impossible to save 30% on your project without saving more in your lighting. That said, let’s take a look at the TRUE impact of lights on LEED points

What is the true extent of designing highly efficient lighting systems?

Let's assume we are comparing to a baseline building that uses 1.3 w/sq ft on (whole building area method) and let's assume the whole building design averages to .84 w/sq ft. What is the savings on this? Well, most people will say, "that's easy, .46/1.3 or 35%"

However, most people forget about the additional savings that comes from lights, especially in a cooling and in heating when the heat is non-electric. Remember, lights give off heat and therefore increase the amount of cooling energy (compressor, fan, and heat rejection).

So, what's the real saving:

Let's assume a VAV system and that lights save on the compressor, fan, and heat rejection with an overall EER of 13.65 (~COP of 4)

.46 w/sq ft = .46 w/sq ft immediate lighting savings

.46 w/sq ft * 1/4 = .115 w/sq ft compressor/fan savings          

Total: .575 w/sq ft actual savings in cooling mode

So, a 35% savings on the lighting yields an effective savings of nearly 45%.

Yeah, but don't the lights provide "free" heat in heating mode?

Let's assume there is gas heat, electricity costs $ .10 kw-hr, and gas costs $1.00/therm (so we will do this in costs). We will also assume a 90% efficiency in heating equipment and 4000 hours of operation.

Using the energy-modeler's unit converter, we find that 1 therm = 29.3 kw-hr

.46 w/sq ft *$.00010/w-hr*4000hrs = $.184 /sq ft immediate lighting savings

.46 w/sq ft /29300 w/thm*1/.9*4000hrs =  -$.070 /sq ft addtnl heating required  

  Net savings of $.114/sq ft in heating mode

So, yes, there is an offset in heating mode but there is still substantial savings as long as the heating is provided using low cost fossil fuels (relative to electricity) or if heat pumps are used in heating mode. 

Furthermore, most commercial buildings have a significant amount of cooling required. Remember, even in economizer mode, additional cooling means more fan energy.

Several sets of data were simulated in eQUEST to see how various cities saved. As predicted, cities with greater cooling showed the greatest savings per watt of lighting saved. It was surprising that even Fairbanks, Alaska had similar savings to climates like Miami. If additional effects, such as summer demand charges are considered, the savings would further increase!


See the calculated data for yourself:

Lighting power cost savings by city
Google Visualization API Sample

Is insulation the best energy saver?

Oct 11, 2010

Is insulation the end all energy saver? In some climates, this is 100% yes, especially climates that need mostly heating, or climates that need tons of cooling. However, proper insulation selection requires an energy model in many cases. Please note that the purpose of this article is to illustrate the importance of energy-modeling and to get users to think about preconceived notions. (I’m sure I’ll get an email from an insulation manufacturer)


Let’s take a look at a climate such as Dallas, Texas:

Like many climates in the U.S.A., it requires mostly cooling, but requires a decent amount of heating. Many commercial buildings do not require any heating until the outdoor ambient temperature reaches 45 degrees F (due to heat coming in the windows, and heat from lights, people, pc’s etc.).


If the building temperature for cooling is 75 degrees, that means there is a 30 degree range - where insulation actually costs more energy (anytime the outdoor temperature is between 45-75 degrees F). In these cases, heat is actually “trapped” inside the building by the excess insulation (kind of like when you jam your entire extended family in a room on Christmas eve).

In a climate such as Dallas, weather data will show that over 4000 hours are between 45-75 degrees F. In other words,too much insulation in the walls is a potential problem for over 40% of the year.
Since that leaves 60% of the year remaining, we cannot simply ignore insulation. However, it means that over-insulating will more than likely result in a greater energy loss, depending on your buildings cooling and heating profile. Thus, there will be an optimum insulation level. In order to determine this optimum number, it is a good idea to use quick analysis software such as eQUEST. A good user can perform several runs in less than an hour. One could simply perform a run, and keep adding insulation, until the energy savings starts to decline. At that point, you will have found your optimum insulation amount

Energy-models are key to successful decisions. There is no possible way you could realize how much insulation is disadvantageous without performing an energy model.