Hello,
I've "grown-up" in the time when energy modeling programs always
existed. I'm curious if anyone that has been in the business for awhile
has any experience using spreadsheets to estimate a building's energy
consumption, and if so, would you be so kind as to share them with me?
I'm not looking to use it on any projects and would not try to hold
anyone liable for any results. I'm just curious as to how people
tackled the issue of estimating energy usage, other than degree days,
before the popularization of DOE and other energy modeling programs.
Plus I think it would just be fun to play around with what other people
have used.
Thank you in advance,
Dan Croisant
Hi Dan,
I believe the approach you may be looking for information on is called Bin
Analysis or Modified Bin Analysis. With this approach, you can use
spreadsheets to estimate energy use based on the number of hours each year
an area spends within a temperature bin. Correlations between
weather-dependent loads (ventilation CFM, CHW loads, HW loads) can be
estimated, or better yet, calibrated using building trends or metered data.
More complex bin models can include detailed envelope calculations,
occupancy and internal load diversity schedules, and regressions that
estimate chiller, heat rejection, fan and pump energy based on part-load
performance data obtained from manufacturers or metered data (existing
buildings) and good engineering judgement. In my experiences, it isn't
uncommon to have an 'occupied' and 'unoccupied' bin model for the same
project.
You may be able to find some ASHRAE literature on the topic on the internet
or through libraries. Unfortunately, I don't have any examples at hand that
I can provide to you for your review.
John T. Forester, LEED AP BD+C
I attended an Energy in Architecture course given by AIA in 1982. I still
have the manual.
The energy calculations section includes a two page worksheet to do a
building block cooling load , a one page worksheet to do a building block
heating load, worksheets for annual heating loads using degree day method
and annual cooling loads using equivalent full load operating hour method,
and appropriate tables from ASHRAE.
Looking it over I got a good laugh out of the last page - circles with marks
around the circumference (0-100) to be used for pie charts to show energy
costs by end use.
I had already started DOE2 (or should I say CAL-ERDA) for several years
prior to the course, but this was run on a main frame, and many people were
doing energy calc's by hand (remember - this was before PCs and
spreadsheets).
Things were very primitive back then.
Mike Andelman
Dan:
As much as I LOVE to spend time (billable?) creating complex and clunkly
fragile spreadsheets to meet my own rapid prototyping energy analysis needs,
I feel obligated to caution you to think very carefully about economics
before using heading down a path of using a spreadsheets developed by
'others' as a basis for much of anything. Your time might be better spent
studying and exploring what is 'beneath the hoods of popular and well
documented whole building energy simulation programs.
Having said that, I strongly believe anyone seriously interested in
mastering skills for estimating building energy should have a strong
understanding of the many available tools, and an awareness of the evolution
of those tools. (*How did we get here?) I can share a few of my favorite
resources developing an understanding of alternatives to 'full blown' 8760
analysis tools and how they work.
1) ASHRAE RP-363: If you are an ASHRAE memeber, consider downloading RP-363
documentation (ASEAM). This text lays out the methodologies for estimating
loads, systems, plants, control strategies and so forth. It's an 'oldie but
a goodie'.
Login -> Bookstore -> Papers and Articles -> Memebers Only Free Access to
Research Projects, Final Reports,
Search for the term "363" - you are looking for this: RP-363 -- Upgrading
Documentation of the Proposed TC 4.7 Simplified Energy Analysis Procedure
Chapter One has a nice section laying out the foundations for some
alternatives to hourly analysis, as well a discussion on limitations. If you
REALLY want to build your own spreadsheet model for estimating building
energy consumption, this book should be in your arsenal.
2) Volume 1 and Volume 2 of the "ARCHITECT'S AND ENGINEER'S GUIDE TO ENERGY
CONSERVATION IN EXISTING BUILDINGS"
http://www.wbdg.org/ccb/DOE/TECH/doe_v1.pdf
http://www.wbdg.org/ccb/DOE/TECH/doe_v2.pdf
These 2 guides were written over 20 years ago and for the ASEAM software. A
suprising amount of descriptive information from these guides continues to
be relevant today . Section 4.2 of Volume one has a nice description if
alternative calculation methods.
Best,
Chris Balbach, PE, CEM, CMVP