Navigating Planet Solar

We must first seek to understand

Having decided that renewable energy, and solar in particular, has the potential to completely change the fate of our planet over our lifetimes and for future generations, we started Solarise.

Our mission“Raising solar energy adoption globally”

We live in very exciting times, where we are seeing daily breakthroughs and records being set - where clean, green solar energy (and other renewable energy sources) are rapidly displacing dirty, non-renewable fossil fuels (coal in particular). And due to rising efficiencies and reducing costs, solar energy is winning the economic argument too, even without subsidies in many cases.

But we know that the transformation is not happening fast enough! (our friends at 350.org make the case clearly enough: https://350.org/science/ )

So I've been studiously analysing the market to understand where we can make the biggest impact. I don't intend for the summary below to be exhaustive, but I think it represents the main avenues being pursued globally at the moment.

I would really appreciate comments from those in the industry to validate, challenge or expand on my thoughts and to help prioritise where you think we should focus our efforts as we begin this noble mission ...

In no particular order:

1. Solar cell and panel product R&D/ bring to market – including Third-generation photovoltaic cells [1]

  • Thin film solar cells – cheaper, more potential use cases (e.g. building-integrated/ within windows), rising efficiencies
  • Multi-junction/layered solar cells – much higher efficiencies by harnessing different wavelengths of the light spectrum (e.g. visible and IR) through multiple layered cells each using different band-gap semiconductors [2]
  • Concentrated PhotoVoltaics (CPV) - sunlight can be concentrated about 500 times using inexpensive lenses
  • Temperature tolerance [3] – cooling of solar cells (e.g. water-based), heat utilisation by combining PV cells with heat based technologies
  • Sun tracking – adjusting tilt of solar panels according to Sun's position, tilt depends on latitude of location and time of year (adjust in March and September)

2. Peripheral product R&D/ bring to market - Storage batteries, inverters, monitors, BOS (Balance of System)

3. Utility Solar energy long distance electricity export using HVDC transmission grid – projects considering solar electricity generation in deserts for long distance transmission (e.g. Sahara to Europe [4])

4. Increasing Residential and Commercial solar adoption

  • Government policy/incentives, micro-generation schemes/accreditation
  • Education, aggregator/comparison sites, business case development
  • Product/system go-to-market and supply chain (including distribution/wholesale/retail)

5. Financing of Residential, Commercial and Utility solar power generation


[1] Solar cells that are potentially able to overcome the Shockley–Queisser (efficiency) limit.

[2] The semiconductor chosen for a solar cell has to absorb as much of the solar spectrum as possible, therefore a low band gap is desireable. However, this is counter balanced by the desire to also have as large a built-in voltage as possible which requires a larger band gap. Therefore as a compromise, a band gap between 1.0 and 1.7 eV makes an effective solar semiconductor. In this range, electrons can be freed without creating too much heat.

The photon energy of light varies according to the different wavelengths of light. The entire spectrum of sunlight, from infrared to ultraviolet, covers a range of about 0.5 eV to about 2.9 eV. The primary reason why solar cells are not 100% efficient is because semiconductors do not respond to the entire spectrum of sunlight. Photons with energy less than silicon's bandgap pass through the cell and are not absorbed, which wastes about 18% of incoming energy. The energy content of photons above the bandgap will be wasted surplus re-emitted as heat or light. This accounts for an additional loss of about 49%. Thus about 67% of energy from the original sunlight is lost, or only 33% is usable for electricity in an ideal solar cell.

http://solarcellcentral.com/junction_page.html

[3] All energy from photons greater than the band gap is converted to heat (~47%).

[4] http://www.trec-uk.org.uk/