Pilot Project for residential SIPPs

On last Wednesday (10 Feb 2010) on our local TV station MBC1 in a local programme called 'Dossier' the following was said by an official of Maurice Ile Durable on the Grid-code.

A pilot project to purchase 2MW of electricity generated through renewable sources like PV, micro-hydro and micro-Wind turnines from households, would soon be launched. As usual there were no commitment on dates and tarrifs. The Maurice Ile Durable web site seems also to be under construction since last year or rather since its went online. It seems that this year another web site has been created. Lets hope we can see our suggestions posted on it.

The official also mentioned that they were expecting production capacities of 3 KW per household which would imply some 600 households would participate.

My apprehension with the Grid code is that there is no information readily available on any official web site. The tariffs have not been made public, why are things moving so slowly? By moving at this pace Mauritians will loose interest in the project.

Show Cases, Installation Sizing and Costs

On the 29 October 2009 the local TV station in its News Bulletin showcased two PV installations

1. In the CEB premises in Rose Hill, 4 arrays of PV panels of a total capacity of 2KW, installer was Infra Solar. The system was in operation since the last 7 months and produced monthly an average of 200KW/h (or 200 units per CEB billing) of electricity. The utility company stated it was an example of a residential PV system, but the grid-tie inverter was not shown and no price was given.
2. In a private company IFS at Ebenes, a system with a capacity of 22KW, and using 4 SunnyBoy grid-tie inverters, installer was Blychem. The system costs was Rs 7Million which brings the price per Watt to Rs 318.18.

Electricity generation through PV is expensive but not as much as people would think and provided the installers or importers are not making easy money with their high profit margins. There are many people who think that by going to China or India and picking up a cheap inverter they would be able to get into the business of renewable energy without realising that the inverter should be approved and certified by the local utility company.

What will make people invest in a PV system is the ability to generate a revenue by selling the surplus electricity at a guaranteed Feed-In Tariff over a number of years. The amount of electricity generated should offset the personal consumption. Taking the example of an household with a monthly consumtpion of 300 units in other words 300 KW/h, the PV panels should be sized at least 5KW which will produce 500KW/h monthly and remaining capacity of 200KW/h will be paid back by the utility company. The monthly paid back should be sufficient for reimbursing any loan taken for the purchase of the system

HOW TO

Basically the following components would be required:

1. PV (PotoVoltaic) panels to turn the sun energy to DC electricity
2. Grid-Tie Inverter to turn the DC electricity to AC electricity (240V 50Hz in Mauritius)

By wiring the PV panels to the grid-tie inverter and the grid-tie inverter to the Grid you are done, you are already feeding electricity to your utility company. Seems simple but you better be wise by knowing whats really happening and the workings of the grid-tie inverter. On the Utility side there is nothing to be done except for the meters which will allow it to pay back your electricity production.

An analogy to what is happening, is water running back in your mechanical water meter and decrementing the counter, except for here in case of malfunction there can only be water spillage which is not as harmful as with electricity there may be risks of electrocution, fire, injury and death.

The GRID-TIE Inverter

There are quite a few features which are mandatory in such a type of Inverter and are required to be compliant with the "Grid Code". The Grid-Tie inverter will synchronise itself to the grid electricity frequency and produce a current with a slightly higher voltage to push back the power to the grid.

1. Electricity generated should only be pure Sine Wave and never modified one.
2. Anti-Islanding: Only when electricity is present in the Grid that it will produce its output. In other words when there is a blackout in the Grid it will shut off automatically, this is a very important feature which prevents Utility personnel from getting electrocuted during maintenance.
3. Protection against: Overload, Short-Circuit, Lightning (using appropriate surge arrestors)

Depending on its design the inverter can require a battery bank or be battery-less, an important aspect to be taken into consideration as batteries are not that cheap and will also need a charge controller.

The PV PhotoVoltaic Panels

There are 3 types of PV panels available on the market with different efficiencies and price ranges. The efficiency is the amount of sunlight energy a panel can transform into electrical energy. On a surface area of 1 square metre there is around 1000W of sunlight energy reaching the earth surface, of course figure is for a clear sunny day at noon.

1. Monocrsytalline panels, efficiency 15~30%, most expensive,
2. PolyCrystalline or MultiCrystalline panels, efficiency 13~20%, having a speckle reflective appearance, and less expensive than MonoCrystalline panels.
3. Amorphous panels or thin film panels are the least efficient and least expensive. Compared to the above 2 types they are flexible.

PV panels are connected in arrays, which can be in parallel or series or even a combination of both, to obtain the desired voltage for operating the grid-tie inverters or charge controllers. The total output in terms of power will be the sum of the individual panels output.