Fuss about solar energy
There have been several letters in your column on solar energy as a solution to Bangladesh's energy crisis. As a photonics device engineer working in the UK and US industry for the last 14 years, I would like to make a few points to clarify the apparent misconceptions of those who seem too eager to jump on to the bandwagon of solar power without fully appreciating the technology, the costs and the eventual benefits to one of the most densely populated countries of the world where real estate comes at a premium price. Many have cited the growing trend in the USA, a country that is 60 times larger and has only twice the population, to use solar power as a reason to embrace it in Bangladesh.
The Sun emits energy in the form of electromagnetic radiation that spans from deep ultra-violet through to far infra-red; 70% of the energy that reaches the Earth falls in the visible spectrum. While the ultra-violet portion of this spectrum is mostly shielded by our atmosphere, the remaining portion reaches its surface in the form of visible light (violet through to red) and heat (infra-red). Technology engineered for capturing both the light (visible and invisible) and the heat from the Sun now exists in the form of photo-voltaic cells (commonly known as solar cells) and heat converters respectively. Photo-voltaic conversion involves the interaction of a photon with an electron inside a semiconductor material to generate electricity. This energy can then be used by any electrical device or transported through the national grid. Thus its transportability, combined with a pre-existing infrastructure to do so makes it a very useful commodity which can be bought and sold. However, the material, fabrication and assembly costs of solar cells are significantly higher than that of the heat converters; for a 3kW system, the costs are in the vicinity of US$15,000 to US$30,000. As a resident of a three bedroom house, I now pay about US$0.08/kWh for my electricity off the grid costing me about US$3/day for my needs (I use gas for my heating needs as it is a more cost-effective alternative). Therefore, the pay back period is typically 20 to 25 years taking into account such an off the shelf solar cell system with a 15% efficiency.
On the other hand, heat converters are relatively simple, less costly to make but provide a less versatile form of energy: heat is captured from the sunlight by coated copper fins and gathered to a central point using refrigerant gases (in much the same way a house-hold fridge works by taking heat away); it is then used to heat water which is circulated around a building to meet heating needs. However, converting this heat into any other form of energy say electrical or kinetic as in a steam engine is very inefficient. Therefore, this technology is limited to use in single house-holds. The capital costs are in the region of US$2,000 to US$8,000. Using an analogous calculation, the payback period is about 6 years.
Given these ground realities of today's solar energy conversion technologies, there are acute implications for a country like Bangladesh. Does going all out for solar energy make as much sense for Bangladesh with its poor infrastructure and limited usable land area as it does for a vast, resourceful and advanced country like the USA?
What about Bangladesh's gas reserves? The cost of a gas turbine generator is in the region of US$60,000 and it can produce 600kW. It has approximately the same footprint as one of today's 3kW solar panel assemblies. Thus gas to electricity conversion capital cost is about US$0.10/W or a 100 times lower than a photo-voltaic solar cell. The payback period would be only a few months. Given Bangladesh has vast quantities of natural gas, surely it makes more sense for it to invest in infrastructure so this energy can be transported quickly from one corner to another. In terms of spatial footprint per unit of power produced, the gas turbine generator is 200 times more space saving than a solar panel, and it can be easily shipped from one site to another. Surely, Bangladesh should be investing in a gas based energy production system. Someone wrote that solar cells could be used to produce 1000MW of power in Bangladesh. Sure. But at 100 times the cost and at 200 times the space needed as a gas turbine generator.
While solar energy may make sense for individual and remote Bangladeshi consumers for simple things like charging cell phones, running a radio or lighting half a dozen incandescent lamps such as in a village home or school that has no grid connection, it cannot be used for running rice mills, water irrigation pumps and manufacturing production tools in factories. Why should the development and industrialization of Bangladesh be held back while solar cells become more efficient (approach 40%) and cost less (through an economy of large scale demand and supply) and begin to compete with electricity costs on the grid? Why should the Bangladesh government give huge tax benefits to foreign made solar energy products that are 100 more costly in real terms to available alternative products? If anything, Bangladesh government should insist on as much of the solar cell assembly to be done in Bangladesh as possible. Bangladesh now has the engineering and manufacturing technology to assemble enough solar cells to meet the needs of the small portion of remote and small-scale energy consumers.
Bangladesh must do what makes the most sense for Bangladesh first. What makes perfect sense for President Barack Hussein Obama's USA does not necessarily makes sense for Prime Minister Sheikh Hasina's Bangladesh.
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