| District Energy
Units,
Measurement,
and Rates
|
Rates
Rates for district heating and cooling service are not easy to find.
Here are some rates from an informal survey:
Please feel free to send in average rates from your own system, which can be posted anonymously if so desired.
Units
Probably the most complex (and thoroughly frustrating) part of district energy is dealing with the
different units used for thermal power and energy. Unlike the electrical industry, which adopted
Watts and Watt-hours as units of power and energy long ago, the district heating industry counts
in Btus, Joules, Calories, pounds (and kg) of steam, barrels and ton(nes) of oil equivalent, not to
mention Watts and Watt-hours. I hope to include several common values whenever these units
are used on these pages, since space is not a concern.
On-line conversion engines are available that can help you convert between different units. I
have listed these but others may also be available. None seemed ideal for all the units used in
district energy, but comments and suggested additions are welcome:
Degree Days
English-Metric Heating Degree Days Conversions, by Henry Manczyk.
While all of these can (easily) be converted to each other, degree days present a much more
interesting challenge. There is no one method of calculating degree days. In the United States it
is the annual sum of the daily difference between 65F and the average hourly temperature
reading, while each European country uses different temperatures and formulas. I do have a list
of these and will put them here in the near future, but I would appreciate anyone who can tell me
how to compare these different numbers. I do have an hourly record of temperature readings for
one year here in Rochester, New York, and will calculate the degree days by each of the different
methods that I am aware of and also put the put results on line here.
Currency and Exchange Rates
Current currency exchange rates for most countries can be found at:
http://bin.gnn.com/cgi-bin/gnn/currency
Time
Wondering what time it is somewhere else? Check out: http://www.hilink.com.au/times/
Numbers and Prefixes
District energy involves a lot of numbers -- energy used, produced, delivered; rates, charges,
profits, interest, return, turnover, sulfur and carbon dioxides emitted (or not emitted) into the
atmosphere. Many people (and I hate to say it, many Americans) cannot deal with numbers. At
least we can make and follow some rules:
- Large numbers
- The digits of large numbers should be separated into groups of three, counting from the
decimal to the left and to the right, and to use a space to separate the groups. In
numbers of four digits, the space is not necessary except for uniformity in tables.
- Examples: 2.345 678; 73 846; 635 041; 600.000; 0.113 501; 7 258
- Small numbers
- When writing numbers less than one, a zero should always be written before the
decimal marker.
- Example: 0.046
- Decimal Marker
- Either a period (.) or a comma (,) may be employed as a decimal marker since both are
commonly used. Typical the period is used in the U.S. and the comma in Europe, but
the context should make either acceptable.
- Prefixes
- Prefixes indicate orders of magnitude in steps of 1 000. Prefixes provide a convenient
way to express large and small numbers and to eliminate nonsignificant digits and
leading zeros in decimal fractions. Since no web browser I can seen can do
superscripts or subscripts, I would recommending using the 10^3 notation for
exponents where necessary. The following are the more commonly used prefixes:
| Prefix
| Symbol
| Equals
| Notation |
| exa
| E
| 1 000 000 000 000 000 000
| 10^18 |
| peta
| P
| 1 000 000 000 000 000
| 10^15 |
| tera
| T
| 1 000 000 000 000
| 10^12 |
| giga
| G
| 1 000 000 000
| 10^9 |
| mega
| M
| 1 000 000
| 10^6 |
| kilo
| k
| 1 000
| 10^3 |
| milli
| m
| 0.001 or 0,001
| 10^-3 |
| micro
|
| 0.000 001
| 10^-6 |
| nano
| n
| 0.000 000 001
| 10^-9 |
| pico
| p
| 0.000 000 000 001
| 10^-12 |
Thermal Power
Thermal Energy
To be continued...
1 January 1997