Rooftop solar panels: our new peaking power generators | RenewEconomy

Rooftop solar panels: our new peaking power generators

The debate on meeting peak demand usually overlooks the contribution of renewables. The CSIRO has shown that a collection of rooftop solar panels, combined with sophisticated forecasting techniques and a small amount of energy storage, can look to the grid just like a traditional fossil-fueled generator.


Demand management has finally entered the political lexicon, as politicians to the left and the right realise that a 20-lane wide power grid has been built to service our energy demands, when one half that size might just as easily fit the bill.

Politicians are reacting because the increasing cost to consumers is finally being passed on to the ruling class in the form of a cost to their political capital. But amid the name-calling, the blame-gaming, the party one liners, and the ducking and weaving, comes the realisation that there are some seriously good alternatives. But what is not widely accepted is that many of these solutions involve renewables.

The common thinking among many energy experts and energy ingénues is that renewables such as wind and solar are intermittent and unreliable, and therefore cannot be relied upon for “baseload” generation, let alone switched on at will to meet the rising peaks.

The CSIRO would like to differ. In fact, says Glenn Platt, the head of the local energy systems team, distributed generation such as tri-generation and co-generation, but also in the form of rooftop solar, can play a crucial part in meeting peaking demand. Far from contributing to the problem, renewables such as solar can be harnessed to provide a solution.

“The traditional view would be to say that solar generation doesn’t have a huge part to play in peak demand,” Platt told RenewEconomy in an interview. “But if you look at peak demand on the wider electricity market, it coincides very well.”

The Australian Energy Market Operator noted in a report last week that in the state with the highest amount of solar PV, South Australia, where one out of five houses (twice the national average) have a rooftop system, 38 per cent of the solar output could be considered to be meeting peak demand.

Platt says the CSIRO has done internal research that across the NEM that suggests solar PV could make a huge difference to peak demand. In commercial instances, where a large office building installs solar on the roof, for instance, the matching is virtually on a 1:1 basis.

Designs for renewable-dominated grids usually describe the use of large solar thermal plants with 3 hours, 6 hours, or even longer storage, delivering the sort of despatchable power now provided by gas plants. These technologies still have some ways to come down the cost curve.

On a distributed, or local level, it is also certain that technologies such as battery storage and electric vehicles will add a new dimension to the challenges of meeting peak demand when those technologies are rolled out in the years to come. The EV, for instance, will be like a battery on wheels, and will be parked at home at the same time as the householders flick on the air-con and the TV and add to the power load. Batteries, including those in EVs, can be topped up using solar energy during the day for use at a later time.

But these are glimpses into the (not-so-distant) future, there are already solutions using current technologies and practices. Banking energy in the form of cold air (or hot air) can be achieved by cooling the air more than initially required while renewable sources such as solar are available, and turning them down when peak demand arrives.

This could be used just as easily with a fridge, as it can with an air conditioning system. Many houses use the same principal with solar hot water. Platt says CSIRO has produced research that a change of 1C in heat requirements can change energy demand by as much as 10 per cent – so by storing that cool air, or changing the temperature targets, could have a significant impact.

These techniques are being used on commercial buildings by a CSIRO spin-off called Building IQ. Its technology is already proving particularly popular in the US, where buildings can be pre-cooled and temperatures managed to avoid, or to respond, to peak demand.

The CSIRO is also testing the concept of a “virtual power station” that links a group of rooftop PV systems on a group of residential buildings and links them with battery. The website – which records the combined output of rooftop solar on 20 houses and council sites, and two battery storage installations in the Lake Macquarie district of NSW – can be found here, and some of the output can be found here.

Platt says the research is valuable. “We’ve been able to demonstrate that with sophisticated solar forecasting techniques, and a small amount of energy storage, a collective of rooftop solar panels can look to the grid just like a traditional fossil fuelled generator. So, instead of buying electricity for $12,000 a megawatt hour (as happens in some summer peaks), we can supply green electrons to the grid very quickly.”

The CSIRO is also leading research into solar cooling technologies. A recent report by the International Energy Agency said solar heating and cooling (SHC) could make a dramatic impact on the world’s electricity grids, providing 17 per cent of all energy required for heating in buildings, industrial processes, swimming pools, and 17 per cent of cooling needs, reducing the need for new generation and cutting peak demand in particular.

Like many of those in the industry specialising in demand management, Platt says “it is gratifying that the issue is getting some broader attention. We feel quite strongly that there are better way to do things. Peak demand is a real issue, and it is clear we are not doing things in the smartest manner – this is a genuinechallenge for the networks as well as consumers.”

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  1. Barrie Harrop 8 years ago

    The future is about distributed energy systems where the consumer uses the energy/water.

  2. Chris Fraser 8 years ago

    A reasonable question is why is domestic household solar only meeting 38% of peak demand. Well it’s probably because home owners want to deploy solar panels most efficiently to garner the best return. For some this means facing them on the north sloping roof of the house to maximise insolation and earn as much sun (and export credit) as possible throughout the solar day. Over 80% of energy generated is between 9am to 3pm.

    However, in some network areas with time of use pricing the cost of consuming grid energy jumps from 21.3c/kWh to over 52.5c/kWh after 2pm. For net metered properties, it won’t be long before somebody twigs and puts their PV on the north-western or western facing roof so get the best return.

    • Barrie Harrop 8 years ago

      Agree Chris for Industry/communities an offer like this which we have designed to take in solar feed–not too much sun at midnight.

      With gas powered gen-sets we are just below the wholesale price of grid energy in Aust and expect that to fall as the price of large wind turbines continues to fall

    • Tim 8 years ago

      Without feed-in tariffs, you also want to maximise PV electricity production to offset your electricity use. For many residences, that won’t be the middle of the day. Maybe both east and west facing panels would do the trick, especially as panel prices drop further?

    • Peter 8 years ago

      Thanks Giles

      In WA with a renewable energy buyback price of 8c compared to a 23c supply cost there is a strong incentive to self consume.

      The effect of households timing their airconditioning to self-consume and by cooling their house prior to afternoon summer peak (4pm) is yet to be tested. The potential peak demand reduction caused by self consumption arresting and reversing the growth in projected domestic aircon loads is yet to be factored into load forecasting.

      Forecasting incorporating solar has recently been introduced by it only accounts only for a discounted solar contribution, but does not account for either strategic panel orientation (NW) or the load shifting effect of self consumption.

  3. colin 8 years ago

    Not a mention of pump storage hydro?

  4. Bill 8 years ago

    There are also phase change materials (which keep a fairly constant temperature) that could be heated or cooled during the day as a way of saving solar energy for later use. These can be incorporated into the walls and ceilings of your house.

    I quite like the idea of charging the car at work and then using it to cook dinner and heat the house up…

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