'Here comes the sun'

Before university I spent a year working with a chemical engineering company making ink. I was a little disappointed to discover that this did not involve farming squid but instead mixing up various combinations of chemicals. I specialised in conductive inks and by far our the fasting growing demand was for solar cells. This hardly makes me an expert but means I have an interest in the area!

Firstly, some basics. Solar cells (or photovoltaic cells) generate energy by the photovoltaic effect. Light from the sun, made up of photons, hits the semiconductor in the solar cells. This excites electrons in the atoms which make up the semiconductor and releases them from the shell. There is a electrical gradient in the semi conductor which attracts the released electrons which then flow: generating electricity (physics online).

Potential energy - image from Solar Spark

The potential solar energy available is enormous: 120,000 TW per day compared to the global energy use of 15 TW per day (solar spark). However, this is the total sunlight hitting the earth so if we wanted to use it we would have cover the earth in solar cells and have them all work with 100% efficiency. This is not possible but it does demonstrate just how much we could utilise solar energy.

Now back to those squid...

Oh I do like to be beside the seaside

Any dreams of a white Christmas this year unfortunately didn't come true. Instead the UK suffered flooding, thunderstorms and power cuts. What is the possibility of using this tidal power and will it provide a economically and socially viable solution?

Machine Current Turbines - courtesy FPS

Most of the research in tidal engineering focuses on harnessing fast moving, tidal streams such as the Severn Estuary which are enhanced by topography such as headlands therefore can provide more energy. There are currently only 15 projects worldwide (Denny, 2010, IEEE).

Here is a brief summary of the benefits and cost of tidal power, summarised from Denny, 2010, The Economics of Tidal Power, IEEE

Benefits - The Ireland Example 

• The capacity credit: the amount of conventional (fossil fuel) generation that could be offset by tidal energy. This is was measured for Ireland and estimated to be about $9 million saving per year and could provide 18% of the countries energy sources. 
• Saving money due to reduced emissions of harmful gases which could save $16 million per year for Ireland. Assuming a price of $30 per ton of CO2, $150 per ton of SO2 and $3000 per ton of NOx. 
• Reduced fuel costs to consumers due to lower running costs of the tidal barrage ($39 million per year). Tidal has a particular advantage over over renewables because it is reliable and fairly predictable.

Costs - The Ireland Example

• Variations for energy demand throughout the day mean that energy generators have to be able to ramp up and down power supply. This requires starting and stopping different components such as turbines and boilers. In a tidal barrage, this can cause huge stress on the equipment and reduces the life expectancy therefore increasing the cost. 
• Variations in tidal maximums require careful monitoring and cycling to ensure there is not a power surge. This could cost anything up to $23 million per year for Ireland!
• Building of the tidal barrage and laying cables on undulating sea floor can be very difficult and increase start up costs.

Total cost analysis from Denny, 2010, The Economics of Tidal Power, IEEE suggests that: 

Benefit = $64 million per year, cost = $23 million per year 

Therefore a net positive of $41 million per year 

However, this DOES NOT include the capital investment costs. The cheapest plan currently available to Ireland is $700,000 per MW of power produced. For energy production to just break even the costs would have to be $530,000. Therefore the current plans for tidal energy for Ireland would not be profitable. 

Ireland is recommended as one of the most suitable locations for tidal barrages and despite this this current plans would not be in profit. Energy production is business. This isn't good business. 

Introducing Renewables

The next focus section for my blog is going to be on renewable energy, this will include a variety of different energy sources which have essentially unlimited supply To start off, just how much does renewable energy contribute to the global energy market?

Renewable Energy Share of Global Energy Consumption 2010

Figure 1 source: Renewables 2012 Status Report, page 20

Figure 1 Summary

• Fossil fuels (80.6%) - coal, oil, gas
• Traditional biomass (8.5%) - burning of wood primarily for cooking and heating
• Modern renewables (8.2%) - divided into hydropower, biofuels, heating and power generating, currently the 'heating' sector is significantly larger than power generation. 

Average Annual Growth Rates of Renewable Energy Production 2006-2011

Figure 2 Source: Renewables 2012 Status Report, page 21

Figure 2 Summary

• Over the five year period between 2006 and 2011, production of all energy types has increased. 
• Growth of the Solar PV cells is significantly higher than any other category in 2011 (74%) and over the five year period (54%).
• The main increases over the past five years have been in: solar PV, solar thermal power, biodiesel, ethanol production and wind power (total = 144% increase)
• Hydropower has seen a very minor increase over five years (3%) but it is one of the biggest contributors to the renewable market.