Can trigen get us to 100 per cent renewable? Yes it can

By Jonathan Prendergast, Prendergast Projects

4 September 2012 – There is much debate surrounding the use of gas to supply trigeneration for lean and clean electricity, heating and cooling to our buildings  to reduce Greenhouse Gas emissions.

For some, it is a cost effective way of making significant GHG emission reductions now, and a sensible mid-step on the way to a low carbon economy. For others, it is a distraction that continues our fossil fuel dependence when we should be moving to 100 renewables.

This article proposes that gas is not just a part of moving towards a low carbon economy, but the key to truly move to 100 per cent renewable energy.

Isn’t gas just any molecule in a gaseous state? Well yes, but the term is used very liberally now, especially in the energy industry. Natural gas or LNG refers to methane and is used for heating and cooking at home, and liquid petroleum gas, or LPG, is propane, commonly used in heating appliances (those lovely outdoor patio heaters), for barbecues or as fuel for cars and bought from service stations.

Gas is commonly thought of as another energy form, like electricity in our grids. But actually, the two are different. Electricity is a way of transporting, distributing and using energy, where as gas is a means of storing energy. This is crucial – the storage of energy.

The clue is in how we measure gas, compared to electricity. We measure gas in amounts or volumes of energy, for example, joules or m3. We generally measure electricity in watts, which is a rate of energy, not an amount.

For most of Australia, our homes and businesses have access to electricity and gas grids out the front door. Gas is flexible, and can sit in the pipes, ready to be used when we need it.

But for electricity, generation has to match electricity use at any time. Our main form of storage is hydro, which generates at peak demand time and pumps water back up top in off-peak times, but it is reasonably limited in Australia.

Moving to 100 per cent renewable energy
Right now the concentration is on greening our electricity grid. Wind farms and solar energy are the primary focus to move to meet our renewable energy target of 20 per cent by 2020.  This is 20 per cent of our electricity grid, not overall energy.

Renewable energy doubters often suggest that wind and solar is intermittent and unable to provide the continuous base load. When it is not windy or sunny, we may run out of energy. In fact, the opposite is true.

As shown by the excellent research project by Melbourne University and Beyond Zero Emission, Zero Carbon Australia Stationary Energy Plan, varying weather patterns across our grids can see solar and wind provide continuous base load energy, once it reaches a certain scale of installed capacity.

The major challenge for renewable energy is dispatch-ability. Being able to ramp up at peak demand times. Solar thermal has some potential to store energy and dispatch on demand, but indeed the code is not cracked yet. And it would risky to rely on one solution to meet peak energy demand. In all things sustainability, no-one is concentrating on one silver bullet.

Battery storage in homes or large thermal storage tanks are also considered to store electricity and dispatch on demand. The deployment of batteries in each house is possible, but would rely on households being interested and incentivised to do so. Both options require significant new infrastructure, and stranding of existing assets.

So, how do we move to 100 per cent renewable energy, if solar and wind can’t meet all our instantaneous energy demands? How can we store renewable energy, and dispatch it on demand?

If gas is such a great store of energy, then the next move must be to green our gas grid.

Renewable gas includes biogas and syngas and can be produced by refining organic matter including green waste, food waste, sewerage and agricultural waste.

The production of biogas from waste products or even energy crops do not disrupt the carbon cycle, and are therefore carbon emission and fossil fuel free. Many biogas plant refineries already exist in Australia, and are used to generate local electricity and heat.

Greening our Gas Grid
It is time to think big.

We need to repeat the same steps we are making to green our electricity grid, to making our gas grid green.

In September last year in Fredericia, Denmark, an important milestone was made for the Danish movement to 100 per cent renewable and zero fossil fuel energy by 2050. A biogas plant was connected to the gas grid, and now supplies gas to users through the local community. Already, 17 per cent of Copenhagen’s combined heat and power is fueled by biogas, but in Fredericia, the extra step was taken to clean and pressurise the gas to make it suitable for integration into the existing normal gas grid.

It is likely that in the short to medium term, biogas will cost more than LNG from the gas grid. But just like renewable electricity, organisation, businesses and residents can choose to pay more if they wish. I’m sure many of the organisations currently operating or investigating trigeneration would like to take the extra step and have zero GHG emission energy.  Especially as it is not possible to meet building energy demands by onsite renewable energy in dense urban environments.

How do we get there?
I suggest the following steps:

  • Australian industry to build capacity in the production of biogas
  • Government funding, through the Australian Renewable Energy Agency and the Clean Energy Finance Corporation to concentrate equally on renewable technologies that use the electricity grid to provide base load, and those that use the gas grid to meet peak demands
  • CEFC to be willing to contribute substantially to getting the first few biogas plants connected to and supplying into the existing gas grid
  • Renewable Energy Certificates to be set up for the gas grid just like the electricity grid to enable the purchase of renewable energy gas by choice
  • A Renewable Energy Target for the gas grid set in the near future, based on research on capacity of Australia to supply products for biofuel over time
  • Property developers, owners and tenants begin to consider requesting consideration for biogas as part of their energy mix

The development of biogas has the following benefits for Australia:

  • It can play a large part in meeting our long term move to renewable energy and eliminating Australia’s GHG emissions from stationary energy
  • It can support further development of embedded or distributed generation and energy efficient trigeneration, to reduce the cost of meeting peak demands
  • Potential regional economic development
  • Utilisation of waste products, especially for the agricultural industry
  • Utilises existing gas grid infrastructure, rather than relying on households to install new batteries
  • Biogas can assist Australia meeting its local gas demand in the face of reducing availability
  • Biogas can be exported
  • Biogas can also be produced using electrolysis  (using renewable electricity), another way of storing renewable energy (such as intermittent wind)

A shortfall in supply?
Australia sits on top of rich fossil fuel resources. Contrastingly, Denmark has been forced towards energy efficiency and wind due to their lack of such resources. When it comes to biogas, we share the same potential due to rich agricultural histories.

According to AGL, NSW may run out of gas in six years’ time. While we still have sufficient capacity for electricity supply, this gives a great driver for moving quickly on biogas.

Due to our existing gas infrastructure, shortfall of supply and the storage properties of gas, it is hard to imagine a 100 per cent renewable energy future without biogas playing a large part. Gas is certainly not the devil in disguise.

This excellent well set out online magazine provides more information on Renewable Energy Gas as part of a 100 per cent Renewable Energy future.

Jonathan Prendergast is the director of Prendergast Projects, which provides energy, technical and commercial advisory services for existing and new development projects.

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