Renewables pushing ahead

Covid 19 may have undermined the global economy and that may impose some temporary  constraints on the growth of renewables, but longer term, as costs continue to fall for most of the renewables, the future looks very good. As my last three posts should have indicted, solar energy is doing well, both for heat, at 470GWth, and for power, with photovoltaics now at over 580 GW globally.  The cost of solar PV has fallen by some 90% over the last 10 years, and further reductions are expected. Power from large ground mounted utility-scale systems, which Lazarus put at $32- 42/MWh, is significantly cheaper (typically four times cheaper) than that from domestic-scale roof top units, given commercial economies of scale, but the later boomed when the Feed In Tariff (FiTs) system adopted across much of the EU, made ‘self-generation’ by ‘prosumers’ economically attractive. 

However, the FiT scheme has been replaced in most countries with competitive tendering arrangements and growth has slowed somewhat.  In the UK context, the FiT system included payment for surplus PV power exported to the grid.  That element has been replaced by a new surplus-power trading market and Smart Export Guarantee (SEG) arrangements.  However, as the Energy Saving Trust has noted ‘according to the Government’s own figures, the SEG scheme will only enable around 3,000 installations of new solar PV systems every year: far below both the previous rates and the levels required to reduce emissions to net zero by 2050’.

Wind power in the race

That is not to say that solar PV will not continue to expand in the UK or anywhere else: indeed most scenarios see PV as accelerating ahead and overtaking wind power in capacity terms. Wind is currently at 623GW.  However, it could be quite a race, and in output terms wind has much higher load factors than PV, so it produces more power/GW.  DNVGL says by 2030 there will be 1.5 TW of onshore wind capacity in place, and 150GW of offshore wind (fixed and floating) installed capacity globally in 2030. They say the Levelised Cost of Energy could come down to $50/MWh for fixed offshore and $70/MWh for floating offshore wind by 2030, although some believe that floating offshore wind could be as low as €40, with 350 MW in place soon. Load factors offshore are already above 60% in some locations and that may improve as floating systems allow for siting further out to sea in deeper water.

All sorts of design innovation are likely for floating offshore wind turbine platforms and pontoons, though spar buoys may well win out overall. There may also be new recycling options for old fiberglass blades, and extra-light & sustainable textiles - lighter than fiberglass. There are also infill options for on land wind farms.  Small wind devices are less efficient than large, tall machines, but smaller, lower, vertical axis devices can supply useful power e.g. in-filling on the same site, they boost its output, although it may make the site look a bit more cluttered.  

Most machines are three bladed propeller-type designs, but two bladed devices use (one third!) less material than 3 bladed designs. However, they need to rotate faster to give the same output. There can also be more asymmetric stress on the hub. A two bladed 6.2MW floating Seawind project is planned off Scotland next year, with more to come later.

Much more dramatically, Kite and aerofoil base airborne wind energy systems have been pushed for some while, although Google /Alphabet has now pulled support for one the leaders, Makani. This despite it having run a test flight of its 600 kW airborne wind generator in Hawaii in 2018 and an offshore test in 2019 off Norway.  Flying turbines with airborne generators may be an eccentric idea, but Shell is still looking at the Makani system, and there are other are other variants, such as kites linked to generators on the ground, and ship towing kites, that may hold promise. So it is maybe premature to write an obituary to the whole idea. And the potential resource in the upper atmosphere is vast.

Wave and tidal power trail behind

Still struggling to get to scale and reduce costs, wave energy projects carry on around the world, like Ecowave’s on shore system at Gibraltar, and the Wave roller off Portugal. In the UK there’s a Cor-Power Ocean ‘wave boost’ review, seeking to upgrade efficiency. However, in general, in the marine renewable field, tidal power is doing better with the UK-French Tiger consortium backing a range of projects, like the big Simec Atlantis/Meygen sea-bed mounted turbines, Orbital’s 2MW floating unit and Minesto’s Tidal kite.

Overall global wave and tidal stream energy production may still be small, but talking it up, Ocean Energy Systems' annual report said that cumulative energy produced from wave and tidal stream sources ‘surged from less than 5GWh in 2009 to 45GWh in 2019’, a tenfold rise over the last decade. Of course, at 500MW or so including tidal barrages, wave and tidal are so far tiny compared with hydro, at 1.2 GW globally, but given climate change, there may be operational problems ahead for hydro, as well as environmental and social impact issues for large hydro projects, as my next post explores.  By contrast, wave and tidal stream projects seem likely to have fewer problems- if their costs can be brought down, as has happened with wind and solar PV. Tidal lagoons and small barrages may also be less invasive than large tidal barrages or large hydro projects, and they might be able to provide some pumped storage capacity. That could be important for grid balancing, if the expansion of large hydro is constrained.

Green energy

The potential for green power does look good, which is fortunate since we will need all the renewable power we can get from wind, solar and marine sources, for direct electricity use, but also for charging EV batteries, and for heating, if heat pumps are widely adopted, as has been proposed. We will also need it for hydrogen production. The role of direct green heat suppliers like biomass and solar and the best balance between the use of green power directly or its use for hydrogen production is still debated, and I’ll be coming back to that in the next but one post – looking the the role of electric heat pumps, after I’ve looked at hydro, which is still the largest single renewable energy source.