When it comes to Ireland's electricity market, there's a lot of talk of renewables, but it might be worth taking a step back to begin this discussion. Ireland is a small country that imports a lot of goods and materials and one commodity which we also import is electricity, the same commodity which features in all our homes and workplaces.

Electricity is the flow of electrons through a conductor. What does this mean? The most common analogy used is water flowing through a pipe. The pressure in the system (which causes the water to flow) is the voltage, the actual flow of water is the current. Increasing the pressure is only useful if the pipes can still carry the water around the system effectively.

Now we can see what voltage and current are, but the units of energy are not given in terms of voltage or current. Power and energy are reported in watts (W/kW/MW/GW) and watt-hours (Wh/kWh/MWh). Power is the ability to do work. Energy is the capacity to do this work. The units are to do with the instantaneous rating, and the sum of these efforts.

## Put on the kettle

You probably want a cup of tea right about now so put on the kettle and the rating of your kettle will help to illustrate this point. Say, your kettle is rated at 1.5 kW, that's 1500 watts (k is kilo) and this is the power required to turn the device on. A typical kettle takes around five minutes to boil so this power rating is required for five minutes to boil the water.

If you continuously boiled it (assuming it still takes five minutes each time), you could boil it a dozen times in one hour using 1500 watt-hours of energy, 1500 W of power for one hour. If you boil it just once in an hour then you have used one twelfth of this i.e. 1500 Wh/12 = 125 Wh of electricity. The typical usage for a household in Ireland is around 4,200 kWh per year which would be the equivalent of boiling the kettle more than 90 times every day!

## The power of wind

When we talk about renewable energy, there is one key player in Ireland and that is wind energy. Wind turbines rotate when winds are strong enough, but won't budge if the wind is not strong enough. If the wind is too strong, the turbine might get damaged.

The turbine acts like a motor running in reverse. Instead of using power to generate a force, we are using force to generate power. The force is the wind's impact on the blades causing rotation around the centre which houses a generator. Moving coils of wire through a magnetic field causes a voltage to build up, which in turn causes current to flow through the wires. This is the basic principle of electromagnetic induction.

So if this form of electricity generation is renewable, why not go all in and put wind turbines everywhere? First, the wind is not always strong enough to rotate these turbines. Secondly, it does not always blow when we want it to boil our kettles. We need storage of electricity or for the grid operator to buy our excess electricity and sell it back to us when we need it. This is setting aside other objections to wind power for example land availability, cost of installation, environmental concerns and other more aesthetic objections.

## The grid

Let's now look at our grid. The grid was built assuming that the current would only ever be supplied to the consumers, so back flow on to the grid (or small scale generation) can be difficult, if not impossible to accommodate, given our current infrastructure. Another way to look at it would be like a courier service. If you try to give a letter or package to a courier who calls to your house with a delivery, you would more than likely get a bemused expression. That is not what the service was designed for. In order to accept goods, you need to have been given a scheduled time and a slot in the van. The van driver also has to have had his system upgraded to accept packages.

So why can Ireland not copy Denmark's success, generating more power from the wind than we need? Our grid is not designed nor capable for large scale variation in generation - and we do not currently have enough energy storage to allow renewables to flourish.

As a nation, we are committed to producing 40 percent of our electricity from renewable sources by 2020.

However, there is another option, which is buying and selling electricity to and from Europe, a process which requires interconnectors. Because of this, Denmark is well placed to export and import electricity as it requires. Plans to build an Irish interconnector to France (700 MW) will help us to follow suit, increasing our import/export capacity from the current east-west interconnector of 500 MW. Part of the solution to increasing our renewable portfolio will be provided through further import and export of electricity.

As a nation, we are committed to producing 40 percent of our electricity from renewable sources by 2020. This is to contribute to an overall 16 percent of all energy use from renewables (including heat and transport). Costs associated with missing these targets have been detailed previously. With plans for a new interconnector, and further pumped hydro in planning, what are the options for increasing our renewable energy production rates? Here are some of the options, how they work and an explanation of where Ireland currently stands in relation to these sources.

## Hydropower

Hydropower uses the potential energy (energy a body has due to its elevation or height) within a body of water. This potential energy is converted to kinetic energy (energy due to motion) as the water is allowed to flow from a height down pipework and through a turbine. The turbine converts the kinetic energy to rotational energy of the turbine blades, which drives the generator. This converts the rotation (mechanical energy) to electrical energy.

In 1929, Ardnacrusha started generating electricity onto the national grid. It cost the Irish Free State £5 million (one fifth of the national annual budget), and provided 96 percent of the electricity requirements of the system. Today, it remains one of the largest producers of hydroelectric power. Unfortunately, we have tapped into the majority of this resource, and hydropower accounts for just over 2 percent of our generation capacity. There are still opportunities for small-scale generation ( less than 10 MW), but this is not utility scale and will encounter issues with grid integration if the power is not used or stored at the location where it is generated.

From an episode of RTÉ's Féach from December 1977, a report on the 50th anniversary of the establishment of the Electricity Supply Board in 1927.

## Wind

Wind power converts the kinetic energy within moving air to a rotation of turbine blades. This rotation drives a generator, which converts the mechanical energy to electrical energy.

In 1997, a 15 MW wind farm was installed in Donegal, but the next farm didn't come along until 2003 in Sligo. Since then, over 1400 MW has been added to the generation portfolio. By 2015, nearly 23 percent of our electricity was generated by wind turbines. In January, Eirgrid announced a staggering two-thirds of total electricity generation from wind. While this sounds great, it is an instantaneous reading. Wind power is a variable resource, and thus needs other sources as back up when the wind is not blowing.

## Biofuels

Landfill gas, biomass, bio gas and wastes can be used to drive turbines in a similar way to traditional fossil fuel powered plants. The fuel is burnt and the heat that is released is used to heat a fluid/gas. This additional energy causes the fluid/gas to flow through a turbine, and again we come back to rotation of a turbine converted to electrical energy. Currently, less than 2 percent of electricity generated in Ireland is from biofuels.

## Solar

Solar photovoltaic (PV) uses the photoelectric effect - the absorption of photons of light leading to a release of electrons - to generate electricity. The flow of these electrons is electric current and this is direct conversion of light to electricity. This is not to be confused with solar thermal, which uses the heat within the sun's rays to heat your water.

Solar PV is receiving a lot of press here recently and grants will be launched this summer to increase residential deployment of these devices, which have plummeted in cost over the last decade (80 percent drop since 2009). In 2017, nearly 4,000 homes had opted for installation of PV to offset electricity costs. Commercial (utility scale) developments still suffer from the same issues associated with other renewables: storage, grid infrastructure and land use. However, it does offer an additional source (sunlight) which can peak at different times to wind energy, thus diversifying the portfolio.

## Offshore renewables

Offshore renewables look to deploy turbines or other devices to harness the power of the oceans. This includes offshore wind energy, as this is a technology with difficulties and increased costs associated with the ocean environment.

Offshore wind energy is similar to onshore, though the installation of these devices is complicated by the environment. There are two main options for support structures and these are floating (like Statoil's HyWind) or subsea base (Arklow Bank). To give an idea of scale, the turbines installed on the Arklow bank are over 120 metres tall, around the same height as an office building with 35 floors or twice the height of the new Google Docks development in Dublin. They are installed in water depths of  3.7 m to 6.2 m (shallow due to the sand bank), and have to withstand severe weather events.

In stream tidal energy uses the same principal as wind turbines, but the fluid turning the blades is sea water, rather than wind. This means that the flows required to drive the turbine are lower as water is denser than air. If you consider the kinetic energy of a moving fluid (energy due to motion), it is a product of the mass and the speed (squared). So using water, or sea water, will decrease the velocity and size required to generate similar energy.