Saving energy on site, part 4Posted: Monday, 27th February, 2012
Our clean, green power
This post is part of a series on our low-emissions, energy-efficient building. Read all the posts here.
This, believe it or not, is an active part of a power station:
It’s the library here at CSIRO Newcastle. As well as being a nice place to sit and work, it effectively powers itself via the square PV cells embedded in the transparent ceiling. These panels here represent less than 3% of the total 120 kW of solar PVs we have on our site, all of which feed power into our buildings.
What’s more, our site is also connected to the grid with a two-way meter, meaning that if we generate more energy than we use we can sell it to the grid like a power station. Generating renewable or low-emissions energy on our site is another way – in addition to the energy-saving features I’ve mentioned in recent posts – that we reduce emissions associated with our buildings. In this post I’ll go through how we do it.
Panels, turbines and jet-engines-in-a-box
Because our site was built to show the possibilities available for low-energy buildings, it showcases a lot of different types of PV technology. The cells in our library ceiling, for example, are building-integrated mono-crystalline PV – that is, cells made of single crystals of silicon that were installed as part of the structure at the time of construction. The auditorium roof, on the other hand, is covered with poly-crystalline PV panels of the sort that can be retrofitted to any existing building.
There are also, of course, the beautiful titania dye-sensitised cells (DSCs) that form part of the wall above the reception atrium and have been featured on the blog before:
The office, laboratory and process bay buildings are also covered in monocrystalline PV panels.
The photo above is from a few years ago – we have built a whole new solar thermal field since then – but in it you can see that we also used to have three medium-sized, 20 kW wind turbines dotted around our site. The one on the left was removed in 2009 to make way for Solar Field 2, but the other two are still there. (Actually, the turbines themselves are down for repair at the moment. They’ve had a history of bad luck which includes having been struck by lightning a few times.)
Two other 1 kW turbines also generate electricity and are useful to our Minigrid research team, whose focus is learning how to make small grids stable even when they have multiple, small-scale renewable energy inputs.
These solar panels and wind turbines are all zero-emissions electricity generators. We also have one last type of on-site generation, though, and while it does run on natural gas – a fossil fuel – the electricity it generates has far less CO2 emissions than an equivalent amount of coal-fired power from the grid.
This is a microturbine which runs on natural gas to produce electricity. Not only is gas a lower-emissions source of energy than coal, but this type of turbine is ultra-efficient – up to 70% – when it’s used both for electricity and as a source of heat. For this reason we tend to run it more often in winter when we can put its ‘waste’ heat to good use for space and water heating in the buildings. We have two of these fridge-sized units which generate up to 120 kW together.
On-site generation vs. energy-saving features
So, now that I’ve shown you how we generate electricity on site, the question arises – how much do we generate in a typical year, compared to how much our building consumes? And which do we get more value from – the energy-saving features we’ve installed in our building, or the extra low-emissions generation we have on site?
The answers may surprise you.
Firstly, generation. Our data shows that in recent years we’ve used an annual total of about 1700 MWh electricity. Of this we generate about 250 MWh ourselves. In other words, we generate only 15% of what we need. In the future, when Solar Field 2 is generating electricity for our site as well, we’ll get closer to meeting the mark, but until then we’re still a long way away from being able to be self-sufficient and sell excess electricity to the grid.
Of the energy we generate on-site in a year, the microturbines contribute the most, followed by the photovoltaics. The wind turbines have had a poor showing recently due to their periods of maintenance.
And how does the contribution of on-site generation compare to the contribution from energy-saving features in the buildings? These recent annual figures tell the story:
In other words, when it comes to low-emissions buildings, the old adage holds true: prevention is much better than cure. That is, it’s easier to have a building that doesn’t need as much electricity, than it is to compensate by installing extra renewable generation.
Keep this in mind when you’re trying to reduce the carbon footprint of your own house. The steps that seem smallest and maybe least exciting – like turning off the air-con whenever you can, installing insulation and shade cloth, changing to LED lighting, and using low-energy appliances – can add up to have the most significant effects.