Saving energy on site, part 3Posted: Tuesday, 21st February, 2012
Our smart gizmos
This post is part of a series on CSIRO Newcastle’s energy-efficient office buildings. Read all the posts in the series here.
When I was living at home with my mum and dad there was a routine they had on hot summer days. Before we left the house in the morning they’d pull all the windows and some of the curtains shut to keep the hot sun out. Then, when the evening temperature had started to drop, they’d open them all to let the cool air through. As a teenager this routine mostly came to my attention when I was roused on for having left a window open during the day.
When I moved out it took me a long time to work out why the house I was renting was always too hot. Grudgingly I came to realise that maybe Mum and Dad actually knew what they were doing with the whole window thing. We didn’t have air conditioning at home then, but the simple practice of opening windows when cool and closing when hot had kept the temperature inside the house pretty comfortable most of the time.
To an architect or engineer, who generally loves to have a fancy name for everything, this type of behaviour – in this case, changing something (opening or closing a window) based on varying conditions (hot or cold times of day) – is called an ‘active energy saving feature’. This is as opposed to passive energy saving features like eaves which generally just sit there without changing after they’re built.
We have a lot of passive features in our buildings at CSIRO, and I outlined some of them in the previous post. But we also have a lot of active energy saving features too – some of which are people-driven (in other words, yes, even in my workplace I am still being told when to open and close windows) but most of which are controlled by computer. Although these little gizmos are driven by electricity, the amount they use (the parasitic load) is far, far less than the energy they save the building overall, making them excellent investments.
Take HVAC, which stands for Heating, Ventilation and Air Conditioning – the system that keeps a building at the right temperature. The default state for HVAC in our building on hot summer days is like most other offices: the air-conditioning is turned on. But we have a computer that monitors temperature in all the different office areas, and compares it to outdoor temperature, and works out when we’d be just as cool if the air-con were turned off, the windows were opened, and the passive features like solar stairwells were allowed to naturally create a breeze through the building. When this is the case, the computer sends a message to all our PCs and an icon in our system tray changes colour to let us know it’s ‘open window’ time. It also opens a few motorised louvres and uses magnetic door stops to latch open stairwell doors.
In addition to considering human comfort, the computer also takes into account the current electricity price. As you are aware this price can increase by over 100 times (not 100%, 100 times) during hot summer days when the grid’s getting stretched to its limit. Our building is programmed to reconsider its need for air-con during these times and is encouraged to try natural ventilation instead. Imagine if most buildings could automatically minimise their energy use in times of high demand – not only would everyone save a lot of money, but we’d be able to band together to prevent blackouts*.
Of course, with this type of building management system, the residents of the building can customise it to reflect their preferences. For example, a manufacturer might have careful temperature control as a priority in their plant building, whereas administrative office workers might be prepared to trade off a few extra degrees’ variation in order to save money on electricity bills or lower their carbon emissions. (More on temperature variation and comfort levels in a later section.)
And in yet another vindication of my parents’ window routine, our building also has a function called ‘night purge’ which is essentially the same thing. If the outside air temperature drops within a certain range overnight, the ventilation fans are switched on and the building is flushed with cool outside air. This reduces the load on the air conditioning when it starts up in the morning – or negates the need for it altogether.
There’s other smart cooling and heating features, too. Our air-conditioned air is delivered not by overhead ducts but through vents in the floor. This means that only the part of the room with people in it is kept cool – why condition the air way above our heads? And the vents are easily repositionable, meaning we generally stick one right under our desks for maximum benefit, and they’re adjustable, meaning you can give them a clockwise turn to customise the air flow rate. Nice.
You can have active energy saving features for lighting, too. One method would be to actively keep reminding people to turn off the lights. But even so, people are notoriously forgetful, so CSIRO opted instead for gizmo-driven features: light-level sensors and motion sensors.
The motion sensors replace light switches, in that they automatically turn the lights on when you’re in the room and turn them off when you’re not. No forgetting to turn the lights out here.
The light-level sensors come into play when the light shelves are reflecting a lot of sunlight into the offices. They detect that there’s a lot of natural light around and tell the fluorescent lights to dim a bit. A ten-percent reduction in brightness that’s not needed, is a ten-percent reduction in energy usage – another easy way to save power.
These are just a few of the ways our building actively saves energy. But as I mentioned in the first part of this post, we’re also working on improving our energy efficiency, and one of the (several) new things we’ll install to do this is CO2 sensors in the few air-handling units in the building that don’t already have them. This is important because if we are running the building on air-conditioning on a given day, it’s much more sensible to recirculate as much of the cooled air as possible and use it again. With CO2 sensors to make sure the air is still fresh enough to recirculate, we can run air-conditioning much more efficiently, and upgrading these three remaining systems will save us around 15,000 kWh of electrical energy a year, with a payback period of around 6 years. To put this in perspective, that’s more energy saved than we generate from the solar panels on our auditorium AND the panels on our process bays per year combined.
This shows that energy-efficiency may not be as glamorous a topic as installing solar panels, but it can be just as – and usually even more – worthwhile.
The solar panels are just one of the types of low-emissions electricity generators we have on our site. More about those and our other on-site electricity generation in the next post.
* this is exactly the sort of thing our Intelligent Grid research group are helping to make a reality in communities.