Processing Weather data is not the problem

As we have seen degree-day calculation example it is not calculating degree-days that is the problem. Much harder is getting a reliable source of weather data.


There is the ideal which explains why we need a pragmatic solution


For synoptic and climatological meteorology, the temperature required is a representative one of the 'free air' conditions over as wide an area surrounding the observing point as possible, with an internationally agreed height (for the thermometer bulbs, sensors etc.) of 1.25 m above local ground level. A fixed height must be specified, because vertical temperature gradients can be intense: for example on a clear, calm night or around the middle of the day with strong solar heating. 

The best site for a screen, or thermometer shield for a land station is therefore over level ground, freely exposed to the sun and wind, but not sheltered by buildings, trees, bushes etc. The temperature sensor must be shielded from direct sunshine (hence a screen or shield) and precipitation (or a dry bulb becomes a wet bulb), and there must be a good circulation of air around the bulb/sensor head. If you have a garden, then the 1.25m above ground level can usually be met with ease. What it usually problematic is gaining sufficient clearance from adjacent buildings, trees etc.

The screen/shield should be positioned over grass (or less preferably, but still acceptable, loose soil), but not compacted soil, tarmac or concrete, as these media absorb and radiate solar energy strongly, and affect the readings quite significantly. 


The bottom line is that the weather station should not be near a building - making it rather difficult to achieve if linked to a building management system


Pragmatically, there are three approaches of which one is reliable, one dreadful, and one relies on luck. First let's reject the "dreadful method".


Using your own local weather data


Just because sticking a weather temperature out of a window and calculating the degree-days using your Building Control System is easy AND VERY LOW COST - It does not make it cost effective.
In fact, though commonplace it is unbelievably stupid!!!  - Why ? - When doing energy management we are seeking to validate decisions in a real context.


If we look at the real context of "demand" as determined by a potentially broken system, we may see that  software does "exactly what it should" given the inputs.  We need to validate the inputs !


Using a free independent source of reliable weather data


This is the one that relies on luck.  Maybe you live next to an air-field.  Air fields and weather conditions have an obvious and important relationship.


Otherwise the typical distance between reliable weather stations is so great to make it meaningless for all but the broadest of analysis (eg. in the UK with a very much higher than average station density the typical spacing averages over 40km).


So if you live near one of the worlds Metar stations http://www.degreedays.net/ can help you (except if you believe that you building changes behaviour between day and night (many do)


Dr Russel Layberry provides some data (weekly resolution via teh Environmental Change Institute in Oxford


http://www.geog.ox.ac.uk/~rlayber/world_weekly_degree_day_data/


And in the UK data is available daily from 77 stations


http://www.eci.ox.ac.uk/research/energy/degreedays-weekly-daily.php


What we believe to be the right approach


If you look at a weather map, it has values for rain, pressure, wind and temperature for every point on the planet. These are calculated using super computers world-wide.  Generally these provide the data against which local weather stations are vetted, and over time average zero statistical error or drift.  Extracting data by Latitude, Longitude and ASl for a building in question is the approach we use. In general this is the best globally available reference data available.  Our partner meteoblue AG of Basel Switzerland provide this to support our commercial client weather needs.


Update - Please note our free service based on public weather data 

Degree-Day Calculation Method

So you decide you want to do a degree-day analysis (or have someone like kWIQly do one for you). - What does it involve - the calculations are not the problem !


Update February 2012 : You can now get degree-days for anywhere on the planet calculated for free by kWIQly


Given a stream of dry-bulb temperatures (normal Celsius or Fahrenheit ignoring wind-chill) - We can write down how we calculate heating degree-days for any particular balance-temperature really easily:


Instructions ...


For each regular temperature measurement in a day write down 0 if
temperature is above balance-temperature. Otherwise write down the difference between balance-temperature and air-temperature. Degree days is the average of all the numbers written down.


Here is a really simple worked example....

Time	Air Temperature	Degree-Load for 15.5 Balance
12:00 AM	12	3.5
01:00 AM	9	6.5
02:00 AM	8	7.5
03:00 AM	8	7.5
04:00 AM	7	8.5
05:00 AM	6	9.5
06:00 AM	5	10.5
07:00 AM	4.5	11
08:00 AM	6	9.5
09:00 AM	7	8.5
10:00 AM	8	7.5
11:00 AM	12	3.5
12:00 PM	15	0.5
01:00 PM	16.5	0
02:00 PM	15.5	0
03:00 PM	14	1.5
04:00 PM	13	2.5
05:00 PM	12.5	3
06:00 PM	11	4.5
07:00 PM	10	5.5
08:00 PM	10.5	5
09:00 PM	9	6.5
10:00 PM	8	7.5
11:00 PM	8.5	7
	Average	5.71

So here we see a day with 5.71 "Degree-Days" of load - It is simply the area in "degree-days" under the horizontal balance temperature line - Shown here in Red - The lower the Temperature (Green)  - The bigger the red area relative to the balance or "on-set of heating" line

Ventilation rates and Degree-Days

"Okay, Houston, we've had a problem here."   The NASA Version


Our problem has very little in comparison with the one Swigert faced on Apollo 13 except perhaps for one thing. It's a systematic problem and it should not be overlooked.


Let's think about what happens when you heat a building (this applies to cooling too).


We can consider two forms of heat loss conduction and convection (we won't worry about radiation) and see how they effect the cost of servicing the building.


Conduction


Some building shell exists (walls, roof, glazing etc) and each of these gradually releases heat proportional to the temperature differential between inside and outside. It is not an instantaneous effect, but is subject to exponentiation. The rate of conductive heat loss is completely unrelated to the rate or temperature at which air enters and leaves the building (ventilation).


Convection


Now lets assume that the building has some form of ventilation. Air is drawn in, used and then rejected by natural ventilation or perhaps driven by fans.


The energy content of air is dependent on its condition (temperature, moisture content and pressure) - this is called it's enthalpy.


When air leaves with higher enthalpy (energy content) than it enters a building, it is carrying energy with it. So with all other things being equal, if you ventilate a building you transfer energy in or out instantaneously.


Conclusion


Now if we assume that a building is maintained in a comfortable condition, we can easily see that the balance temperature (the outside temperature at which we need to attempt no deliberate heating or cooling) is dependent on internal unintended heat gains, on conduction, AND on convection (forced or otherwise).


In short, the balance temperature of a building varies with the rate of ventilation. The fundamental assumption that a building has a fixed balance temperature (essential to underlying theory of degree-day analysis) is flawed if the building is ventilated at different rates at different times.


Offices, Theaters, Hospitals, Sports Halls - All of these are affected.


To point out that Degree-Day Analysis assumes at its' very core that a building has negligible thermal mass (no concrete !), is infinitely ventilated, and has perfect insulation, would be taking this a step too far (though true).


The point made is that Degree-Day Analysis is a very inexact science, based on absurd assumptions that none-the-less provides very useful information if used with sufficient care!

Update February 2012 : You can now get degree-days for anywhere on the planet calculated for free by kWIQly

EU Energy-Using Products - Environmental disaster?

What's the problem ?

The Energy Using Products directive from the EU implies amongst other things that from 1 January 2015, all electric motors from 7.5-375 kW must either meet the IE3 standard or the IE2 standard equipped with a variable frequency drive (VFD).

Grundfos supported this initiative, as well they might and credit is due (in general).

However, there is also significant scope for this specific requirement to cause an environmental disaster...

This sounds rather alarmist - it is, I am sounding an alarm!

However it also requires that I justify my position.

As we see on the left slowing a pump just a little from 100% - 60% of maximum may reduce energy consumption by 80%

This is not to be sneezed at.

But system efficiency is another question - and it is the only question that matters from an environmental perspective.

If we consider the most common application of pumping it is in the movement of energy contained in hot heating services or cold chilling services water.

A pump capable of moving megawatts of heating water (powered say by gas boilers or furnaces) may be pumped by a few kilowatts.

Under these conditions reducing the pumping rate saves some kilowatts, but may have repercussions on the supply of megawatts of services.

But is this likely?

Lets see what the International Energy Agency have to say on the subject:
IEA (experiences in Swedish District Heating) (Abstract)

In practice, the achievement of large temperature differences is counteracted by mal-functions of consumer stations and their components and often also by short circuits in the distribution network, leading to higher return temperatures and in general also to increased supply temperatures compared to what would be desirable. Additionally, system designers have very often built-in over-dimensioned "reserve capacities" leading to non-optimal functions of control instruments. The results of such malfunctions are higher pumping losses, higher return and supply temperatures and therefore higher heat losses from the net. In the worst case, the net can be choked at the high load times and will not be able to deliver the necessary design power.

What does this mean?

OK - Imagine you are controlling the mixing of hot and cold water running into your bath in some cheap motel. The hot water is scalding hot (unnecessarily) and so you keep the hot tap pretty much closed at all times.  All the other guests do the same. So what happens is very little very hot water is used, and as a result the motel saves pumping costs with their new variable speed drive (for the technically alert I am assuming an open system so local pumping is related to water flow delivered). 

 BUT - a smart new engineer comes along and says, 

"HEY - I have a better idea - If we lower the water temperature, we will save on gas, and less heat will leak out of the hot pipes into the areas we are cooling. Naturally, guests will use a bit more water, which will put up our pumping costs, but these are negligible vs our heating costs."

Our new engineer is using the variable speed drive as a feedback mechanism to better control provision of the primary service "heat",  by ensuring that the VSD never works as intended (ie operates near maximum rated output - where there are nearly no electrical savings) he maximizes system efficiency and hence environmental impact. In other words, generally the best VSD is one that is not installed as intended !

Conclusion

Where-ever a VSD is fitted, without a smart engineer like our fictional character above, at times of low load, simple thermostatic control efficiency is jeopardized, because the returning temperature of hot or cold water services is no longer indicative of the demand for those services. 

Simple return temperature sequencing of boilers and chillers as recommended almost universally for simple system control by Best Practice (to overcome the single weakest point in any building with multiple boilers - the matching of supply to demand), becomes not a simple panacea, but an unstable control system with an inherently non-linear destabilizing positive feedback mechanism built in.

And that is a Environmental Disaster - not one that is waiting to happen, but one that is already well underway !

Update : There is good reason for use of appropriate technologies when adequately understood and outlined here :

http://www.abb-conversations.com/2012/11/three-steps-to-improve-compressor-energy-efficiency/trackback/

Seth Godin - After you've done your best

Seth godin:after youve done your best is a great short post about learning from failure.

He writes

 "Learning from a failure is critical. Connecting effort with failure at an emotional level is crippling. After all, we've already agreed you did your best."

I think running a business is a little like trying to manage the relationship between Faith and the Science
Each seeks the truth in a different way (we can think of Truth of a viable business model where "We are a going concern" is the acid test).

Faith in God is usually based on our assumption that there must be an answer.  To think anything else of this wonderful little planet and our experiences feels horribly nihilist...
we're-99-certain-this-is-the-most-beautiful-footage-of-earths-auroras-yet-recorded

or this



However

 In the same sense a Business Leader must be a believer that in some way his or her company, has value. (S)he must hold fast to this even in the throes of the Startup Roller Coaster : Mark Suster  when it can feel that there is room for doubt as you feel the stomach lurching abyss open up yet again.

This faith starts with an assumption of about what our business must look like - The business vision (in our metaphor this is of a loving, infinite omnipresent eternal creator God). These are Axioms Axiom (Wiki)  that cannot be dis-proven - which is what makes faith inherently non-scientific but simultaneously as reasonable as any alternative. A business-person is thus a "faith leader" that time may disprove (the runway).

Science starts with a similar premise or Axiom (That there must be a single factual truth of events, causes and effects that exists if it can be uncovered).  It proceeds by way of Occam's Razor  paring away at the falsehoods by experimentation, and assuming what is apparent and sufficient to explain experiments is true until dis-proven (these are hypotheses  - they become Laws at IPO but can still fail)

Searching for the truth in these two ways should converge - (like carving a statue - A sculptur works long and hard before people will put it in the Louvre ). The little experiments gradually erode what is not useful or not valid until a core truth (the Minimum_viable_product) is exposed.  If the experiments show that the axiomatic business plan does not work the founder must pivot (change belief).  There is nothing wrong with this.

A business leader MUST be flexible enough to change anything (even his most cherished beliefs) when the best is not good enough.

The same is true of a faith leader - If you can disprove something that is necessary for a faith, the faith must bow or it will break.

There is a perfect purpose to existence and my running an imperfect but continually improving business hopes to serve that purpose. I rejoice in all the entrepreneurs who work so hard and risk everything to show that their vision of a business is true - and only experimentation can ever show them wrong.

I also rejoice in my existence on this planet - and must believe that there is a reason Logos for it - The wonderful thing is nobody can prove this wrong (though I must learn to be better) and I think that was the major point of Seths brilliant post ...

"Successful people analytically figure out what didn't work and redefine what their best work will be in the future. And then they get back to work."


Must get back to work - speak later :)