“Imagine a time when every rooftop in the world has a solar panel on it. Looking at Google Earth, all the rooftops you see would have panels. Panels would provide power or heat, or both.” Dr Eric Martinot calls this vision “no rooftop left behind.”
Putting solar panels on virtually every rooftop worldwide is entirely possible. Dr Eric Martinot, senior research director with the Institute for Sustainable Energy, and adjunct professor at Victoria University of Wellington, estimates there are already 15-20 million rooftops worldwide bearing solar power (photovoltaic, or PV) panels, primarily in residential and commercial buildings. There are more than 90 million rooftops worldwide with solar hot water/heating systems installed, primarily in China. Here are five ways he believes we can progress towards a solar powered future.
1. Growing global markets
“Most people don’t realise how fast the market for solar PV has grown,” says Dr Martinot. In 2003, the global market for PV was 1 gigawatt (GW). But by 2013, global solar power (PV) capacity was around 140 gigawatts (GW). Roughly 40 GW of solar PV was added in 2013 alone, which translates to something like 400 rooftops per hour. By comparison, all the nuclear power plants in the world total around 350 GW.
2. Policy-led growth
The growth of solar PV has been driven by a variety of policies, including capital subsidies, guaranteed prices from feed-in tariffs, or net metering, which allows customers to offset consumption. Some cities in Europe have policies or mandates for solar PV on new construction.
These sorts of policies are instrumental in bringing about major economies of scale in manufacturing, which, along with improvements in technology, have lowered the cost of solar power.
3. The competitiveness of solar PV
“Grid parity” means the equivalence of solar PV generation costs with retail electricity prices. Grid parity can be distorted because of subsidies and a variety of electricity market factors, such as differential prices, seasonal pricing and net metering rules.
In its 2013 World Energy Outlook, the International Energy Agency pointed out that grid parity may not mean economic competitiveness, because solar generators must still pay their share of fixed grid costs, even if most of their power is self-generated. This is only true under a policy model in which ‘stranded assets’ – the generation, transmission and distribution infrastructure rendered unneeded by the growth of distributed solar power – must still be paid for by all consumers equally.
In countries with fast-growing demand for power, the issue may be moot, as solar PV slows the need for grid investment. In places with high electricity prices and good solar resources, such as Spain and Hawaii, grid parity is being reached, even without subsidies. “Rooftop solar will become competitive without subsidies in a growing number of locations around the world, provided that the policy challenges ahead are addressed,” says Dr Martinot.
4.Innovations and challenges ahead
The main innovations and challenges ahead for rooftop solar relate not to the technologies themselves, but to innovations in business and finance, policy, and integration.
New business and finance models
A variety of finance models have emerged, including leasing, fee-for-service, and pre-paid. Some models allow renters rather than owners to choose solar, and many of these new innovations have been gaining mainstream acceptance by commercial financiers.
A new generation of power-sector policies and market rules
Policies must shift from cost- or price-based support for renewables to defining new rules and market structures for electricity. There is some urgency for this, as established power companies suffer large financial loses on generation and grid assets due to the influx of renewable power. Those losses are leading to growing resistance to renewables by some of these companies, not for technical reasons, but for financial ones.
Materials and systems integration
In 2012, only about 1% of the global solar PV market was for so-called “building-integrated” PV. However, the integration of solar PV into building materials, such as roofing materials and glass facades, represents an important innovation trend.
5. Overcoming objections and myths.
“The lights will go out.” “There are not enough raw materials.” “There will be no power at night.” “How will we generate power on cloudy days?”
These are common objections to solar power. Dr Martinot does not believe that solar power is a panacea.
“Still, solar presents a singular opportunity for distributed energy, for autonomy, for communities, and for entire cities. Most would allow that future energy systems will be a combination of centralized and decentralized, along with intermediate levels like district energy system,” he says.
However, solar power presents the opportunity for visions like “no rooftop left behind”.