Highway solarisation: World’s first carbon negative electricity generation technology?

Carbon negativity

When a certain product could be manufactured with absorption of greenhouse gases – mainly CO2 – we call such a substance a carbon negative compound and one of the first products we came across in this category was the foam rubber mattress made out of natural rubber latex. 

When Nippon Nature Foams wanted us – Somaratna Consultants – to calculate the greenhouse gases emitted in its manufacture from natural rubber latex, its management team, comprising mainly Naushad Mohideen, Chaminda Serasinghe and Dr. L.M.K. Tillekaratna, was confident that what they were manufacturing was a carbon negative product. 

When we calculated the GHG emissions associated with this product as per ISO 14064-1 Standard – the first such initiative carried out in Sri Lanka – we found out that it was truly a carbon negative product. Ever since then, Naushad and Serasinghe pursued their work on carbon negative products and kept on promoting carbon negativity as a forceful approach to mitigating climate change.

The justification for the concept stems from absorption of CO2 from the atmosphere in the formation of the rubber latex in the rubber tree. Since the tree absorbs CO2, rather than generates CO2, in the production of latex, the latex takes this carbon negativity with it to the final product. Depending on the processes involved in the conversion of latex into the final product, the CO2 already absorbed may be adequate to nullify all the CO2 emissions involved in the subsequent processes to yield the carbon negative product. Natural rubber foam is such a wonderful product.

Highway solarisation

When we developed highway solarisation – that is laying photovoltaic solar panels above and along the highway – to generate electricity to charge battery electric vehicles or to supply to the main grid, we knew that it is a carbon negative product in a broader sense. 

The significance of carbon negativity stems from its usefulness in negating climate change or global warming. The manufacture of a carbon negative product reduces or negate climate change. Highway Solarisation generates electricity without generating CO2 or other greenhouse gases. But of course, the manufacture of the photovoltaic solar panel, the manufacture of steel structure, cabling, inverters, transformers, etc. involves generation of greenhouse gases. 

According to a paper read by Antoine Beylot, et al on ‘Environmental impacts of large-scale grid-connected, ground-mounted PV installations’ at the World Renewable Energy Congress 2011 – Sweden, greenhouse gases generated in association with (i) photovoltaic solar modules, (ii) foundations, (iii) system end-of- life treatment, (iv) supports, (v) supplementary infrastructure, (vi) electric infrastructures and (vii) installation would all add up to 53.5 gCO2e per kWhr. 

In other words, the above mentioned components and activities of a normal PV solar park installation would have resulted in the generation of a certain amount of greenhouse gases, which when distributed over the entire life time of the plant would yield this 53.5gCO2e per kWhr to be generated.

When PV solar panels are installed above an existing highway each one of the resulting kWhrs would be the result of (a) an equivalent 53.5gCO2e per kWhr emitted during manufacturing/installation processes as well as (b) the prevention of the absorption of a certain amount of solar radiation by the highway during the operational phase. 

Since the CO2 generated/emitted by any process brings about global warming/climate change only by way of radiative forcing, expressed in W/m2, resulting from such CO2, we reason out that any reduction in the absorption of solar radiation by the highway itself – which absorption would otherwise have resulted in radiative forcing – should be convertible to an equivalent reduction in CO2 emissions.

If this estimated reduction in CO2 emission into the atmosphere is more than the above mentioned 53.5gCO2e/kWhr, highway solarisation is a carbon negative way of generating electricity. It is in order to check the validity of this claim, we carried out the following calculation.

Carbon negativity of highway solarisation

In Sri Lanka, the average solar radiation intensity is, say, 5kWhr/m2 day which could also be expressed as 208W/m2. The absorptivity of solar radiation of the bituminous surface of a roadway is about 90%. A PV solar panel will convert about 14% of incident radiation into electricity and reflect another 14% of solar radiation incident on it. As such the percentage of incident solar radiation which will get absorbed and thus contribute to global warming will be only 72%. Thus the highway solarisation process reduces this percentage of solar radiation getting absorbed and contributing to global warming by 18% or by 37W/m2.

To bring in a radiative forcing of 37W/m2, we would need an increase of 2642ppm/year in the concentration of CO2 in the atmosphere, if we use the value of 0.014W/m2. ppm CO2 given in International Panel for Climate Change Technical Assessment Report No. 4 for the radiative forcing per unit ppm increase in CO2 concentration in the atmosphere over one year. This increase of 2642ppm/year concentration of CO2 in one square meter area is equivalent to the generation of 39 kg of CO2 per m2 per year. If we need four km of roadway of 20m width to generate 10MW of power, the total equivalent amount of CO2 that would be saved per year will be 3162t.

If we assume that the total number of hours of solar radiation available per year is 1,400, then in one year this 10MW highway solarisation set up would have generated 14 million kW hrs of electricity. As we mentioned earlier, if establishment of a normal PV solar set up would have a green house gas load of 53.5grms of CO2e per kWhr, the total greenhouse gas load of the 10 MW Highway Solarisation unit will be 749t/yr. As such highway solarisation would bring you electricity at a total carbon negativity of 2,413 tons of CO2e per year per 10 MW plant or 172 grms per kWhr of electricity. It is worthwhile to note here that this is in addition to the amount of CO2 prevented from being emitted in the generation of electricity using fossil fuels as being practiced today.

This research is not funded by any national, international, public sector or private sector establishment, nor by any climate change-based funding, and thus resource constraints might have contributed their own share of inaccuracies to this calculation. But this difference between the carbon positive component of 53.5grm of CO2e per kWhr and the carbon negative component of 225 grms of CO2e/kWhr is adequate, we believe, to compensate for such inaccuracies probably arising from (i) asphalt road surface absorbing a solar radiation component less than 90%, (ii) the solar panel reflecting less than 14% incident radiation, (iii) carbon positive component of highway solarisation is more than 53.5 grm of CO2e per kWhr due to the additional structural components that would be needed or(iv) a higher amount of electricity being generated, etc. As such I emphasise that highway solarisation is definitely a carbon negative methodology for generating electricity and it may be the first such mode of electricity generation in the world. 

The other beauty of this methodology is that it generates electricity or rather energy where energy is being used for the most wasteful and damaging – in terms of amount of waste heat generated, amount of greenhouse gases generated – application of fossil fuel combustion. This wasteful application where 80% of energy in the fossil fuel is just wasted is none other than road vehicular transportation.

Relevance to transportation

Transportation as a consumer of fossil fuel energy has some peculiarities as follows: (i) The energy is used in a distributed fashion, (ii) The rate of consumption of energy changes all the time, (iii) The demand for energy is also distributed, (iv) Difficulty in using efficiency enhancement techniques, (v) Locations of usage themselves are moving, (vi) Energy is stored for future usage. This makes it difficult to identify a suitable mitigation solution for greenhouse gas generation from road transportation.

But for the fortune of mankind there is a carbon negative way of generating energy to satisfy such a peculiar demand and that way is called highway solarisation.

Then there are a few issues that need to be ascertained before declaring adequacy or the capability of highway solarisation. One important aspect is the adequacy of the resource itself i.e. do we receive enough solar radiation to fulfil this demand? Of course, the answer is a very emphatic yes. In a normal day we in Sri Lanka, receive about Rs. 3.25 trillion worth of solar energy at the rate of Rs. 10/kWhr; this value is equivalent to 4 months GDP in 2013 and this amount of energy received in a day is equivalent to about 10 years of energy consumed in transportation at the consumption rate in 2012.

Then the next question is, do we have enough highways to be solarised to obtain this quantity of 125 PJ of energy to be used in transportation? What we need for this purpose will be about 10000 km of 20m wide road ways. With the prospect of new highways been built, this amount of road surface will be available for this purpose and we also need to remember that this 125PJ of energy from liquid fuels used for transportation we talk about also includes energy used for railway transportation. 

There had been several discussions about the electrification of railways and anybody looking at the railway lines in a map of Sri Lanka will readily notice the reasonable extent of these lines which are very close to the roadways. This closeness prompts us about the prospect of using electricity generated via highway solarisation even for railway electrification and railway stations could easily be used as storage areas for storage batteries where we can store electricity generated via highway solarisation for usage during those times when solar energy is not available.

In our opinion, this is the ideal time to embark on projects of this nature because the lower oil prices will save us some money to invest in these before the oil prices start going up. On the other hand such action will also put the pressure on fossil fuel marketers to think twice before they start increasing fossil fuel prices.

Highway solarisation – Sri Lankan context

I strongly believe the Sri Lankan energy planners, who have the best of software available at their command should start looking for strategies to (a) exploit the strengths of solar energy available and (b) make weaknesses of solar energy irrelevant, instead of enumerating the well-known weaknesses of solar energy at each and every forum they attend.

I know for sure that this expectation of mine will remain a hope never to be fulfilled. Why do I say that? You only need to look at figures 5.6 (a) and (b) on page 5-8 of the Long Term Generation Plan 2015-2034 of Ceylon Electricity Board to understand the respect these planners have for this invaluable free energy we receive daily. Maybe that this energy coming free is a problem. According to the graph in Figure 5.6 (b) a 10MW PV Solar Plant at Hambantota can generate much more than 44 million MW hrs or 44000 GWhrs of electricity in an 8,760 hr year. This amount of electricity is more than three times the total electricity we, Sri Lankans, consumed in 2014.

Why do I mention this here? To convince the national planners of this country that they should never, ever listen to these energy planners at least in respect of this renewable mode of solar energy we receive for free daily. This particular graph was provided by the Sri Lanka Sustainable Energy Authority to the planners at CEB and they also have blindly inserted the graph into their Long-Term Generation Plan which was then submitted to the Public Utilities Commission. These planners seem to be hating carbon negativity and they seem to love carbon positivity.

Of course, highway solarisation has one drawback. It is not the opinion of a Professor from a foreign university. When the whole world – IPCC, World Energy Council, Japanese and German Automobile manufacturers, etc. – were all wondering whether to back the Battery Electric Vehicle (BEV) or the Hydrogen Fuel Cell Vehicle (HFCV) or the Pluggable Hybrid Electric Vehicle (PHEV), we were very bold in our pronouncements that Battery Electric Vehicle would definitely be the ultimate winner and highway solarisation powering the BEV would lead to a new mode of transportation which we called zero emission transportation. 

We wrote a very emphatic article to the local papers on 3 February 2011 where we compared CO2, H2O vapour and waste heat emitted due to HFCV, PHEV, the Grid Enabled Electric Vehicle and Renewable Energy Enabled Electrical Vehicle to show that the last one when powered by highway solarisation would be the ultimate winner. This was a few months before Prof. Henry Lee of Harvard Kennedy School published the outcome of his mathematical model study that Battery Electric Vehicle would beat the HFCV, PHEV and the Hybrid vehicle. When we wrote to Prof. Lee about BEV powered by highway solarisation, he wrote back to say that he had not looked at the particular aspect of providing power to the BEV.

Most importantly when UN Climate Summit in September 2014 established the three objectives of (a) 30% of new vehicle sales to be BEVs in 2030, (b) need for these to be powered by renewable energy and (c) deforestation to be 0% by 2030, it was promoting BEVs supported by highway solarisation, a stand which we have been promoting since 2008.

Conclusion

Highway solarisation is a unique way of generating electricity which is truly carbon negative. By adopting highway solarisation, we could also promote our exports as been manufactured using a carbon negative mode of electrical energy. This will enhance our chances of exporting apparel to the US and the European countries where the young and educated consumers are deeply concerned about climate change. By using vehicles which are powered by electricity generated using highway solarisation, Sri Lanka can also promote truly green tourism. 

So it is time for Sri Lankan planners to make use of this truly Sri Lankan solution for climate change due to transportation and promote it globally or at least locally and, more than anything else, demonstrate this mitigating solution for climate change due to energy generation and transportation.

(The writer is Managing Director of Somaratna Consultants Ltd.)