PV (Solar electricity)

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Making your own electricity

On this page you can read a about my experiences with making my own electricity on my own roof. In 1997 I started with one PV panel of 104 WattPeak (Wp). At the moment I got eight PV panels with a total capacity of 1100 Wp, which generates about 750 kWh per year. That is about 35% of our electricity consumption.

The installation history of PV-panels:
- Ocober 2003: 4 Philips panels, à 125 Wp = 500 Wp.
- November 2002: 4 Solarworld panels, à 150 Wp = 600 Wp
- October 1997: 1 Shell panel van 104 Wp.

On this page I give per type PV-panel a short technical description and how these panels are mounted on the roof. Next I give the energetic and financial benefits of the PV-panels. Finally I give a view on the differences between a solar water heater and PV-panels, about the costs, required space, installation and the profits per square metre roof.

The four 125 Wp Philips panels

Beldezon supplied this system, which consists of:

Installation of the four Philips panels

Oriëntation

The four Philips panels of 125 Wp each, are placed on the dormer on the front of the house.

Here you can find photo's of some details of the philips panels. Click here for photo's of the assembly of the first set of four Philips panels of my neigbour.

The four 150 Wp Solarworld panels

Beldezon supplied this system, which consists of:

Steca

Installation of the four Solarworld panels

Oriëntation

There was enough space for three solar panels on our own side of the dormer, which we share with the neighbours. Then, one panel had to be placed somwhere else. However, our neigbours offered a part of their roof to place two panels. In this way all the four panels could be placed on the shared dormer.

Photo 1: Two solar panels are already installed. Every panel is mounted on two aluminum rails. One rail for the 3rd panel is already assembled, and one hook, for the second rail can be seen. Some roofing tiles are not yet replaced, so the red-black electric wires of the first two panels are visible.
Pay attention: By replacing the tiles, some tiles have to be placed partly over the hooks. In some cases the hooks lift these tiles a bit. Standing on those roofing tiles (or the tiles nearby) results almost certainly a broken tile!

Photo 2: All four solar panels are installed. Ready to produce electricity.

Photo 3: All four panels, seen from below. Also the collector of the solar water heater can be seen.

The Shell panel

In 1997 I bought one Shell 104 WattPeak (Wp) solar panel. See also this article (ca 350 kB, in Dutch) of the Dutch Greenpeace Magazine of 1998.
Unfortunately this panel had to be removed in 2003 to make place for the four Philips panels. In May 2008 this panel is placed on the roof of the neighbours.

The inverters

Originally the solarworld panels came with four OK4E inverters (see Photo 4a). Unfortunately the quality of these inverters was not sufficient enough. Beldezon has replaced these four inverters for free (!) in 2006 with two 300 W Steca inverters. These Steca inverters look similar to the Philips inverter of the 4 Philips panels. Now I have coupled these three inverters (see Photo 4b).

Photo 4a: The old connection to the grid. De red-black low voltage wires come directly from the solar panels. The low voltage direct current is inverted by the four inverters in 220 volts alternating current. A multiple socket collects the current from all four inverters. The currect flows via a kWh indicator into the wall outlet.

Photo 4b: The new connection to the grid. De red-black low voltage wires come directly from the solar panels. The low voltage direct current is inverted by the three inverters in 220 volts alternating current, connected to kWh meter and a separate fuse.

Measuring the production

PV panels work in silence. Without a measuring device any control is absent about the operation and production of the panels. And what is more fun than knowing that your panels are doing ?

There are many measuring devices available. Some just show that your system works, other give you constantly information on what is happening on your roof, including the present power in Watts, and the share of PV power in relation to your actual consumption of your household. The site from Floris Wouterlood gives a good view on the possibilities of measuring devices. Since October 2005 I am the happy owner of the Eclipse from Beldezon/Ecostream. A quite expensive device, but having a lot of possibilities.

The Eclipse

The eclipse of Ecostream, sold by Beldezon is a solid and many-sided device and informs you of the actual power delivered by your PV system. Also the daily, monthly and annual electricity production can be shown. Besides all these function, this device also can show the same for the electricity consumption of your household. The Eclipse stores daily the measured data in its memory. The own electricity use of electricity accounts about 1 Watt (that is about 8 kWh/year). The expected annual electricity production and the maximal produced power can be chosen, so the scale of the display is used efficiently.

Photo 5: My Eclipse working at a sunny day in august 2006. The consumption side of the Eclipse is not connected yet.

The Eclipse is ' the' device which measures nearly everything what you want to know as PV-owner. However, there are some disadvantages. Besides the Eclipse also one pulse-meter is required. The Variwatt contains such a pulse-meter and can perfectly be used to work in combination with the Eclipse. To measure also the electricity consumption of your household a second pulse-meter is required. Mind that this second pulse meter had to be able to measure relatively a high power and has to be connected by a certified electrician, because it has to be placed between the main electricity meter and the fuses.

Costs: The Eclipse costs about 400 euro, exclusive the pulse meter, about 75 euro.

The Sunny Beam

Kees Bleijenberg has 12 PV-panels and an inverter from SMA; the Sunny boy 2100TL. SMA sells also a wireless monitor which can be used in combination with most SMA inverters; the Sunny Beam. The Sunny Beam displays real-time power output for up to 4 individual inverters numerically and graphically. It also stores a month's worth of production data for review at any time. With software form SMA the data can be written to a computer via an USB connection. Awizon sells the Sunny beam fro about €325,00 euro (2009).

According to Kees Bleijenberg the installation is very easy. Open the inverter, push the print of the radiounit (the Piggy back) in the connector, mount the antenna in the opening for the cables and close the inverter. The software is less easy to use (Sunny Data Control), but a combination with Sunny Report (download at the site of SMA) a nice overview can be made. An another review can be found at solar-review.com

The Variwatt

The Variwatt of Beldezon is a simple device which only measures the produces electricity (in kWh) . It has to be placed between the 240 volts connection of the PV-system and a socet. The own electricity use of the Variwatt is very small (<1Watt).

My Variwatt is in use to measure the production and foresees the Eclipse of data. I connected the two pulse contacts of the Variwatt with the Eclipse.

Costs: about 100 euro

The energy production

The electricity meter runs backwards

Because the solar panels ' pump' electricity into the grid, the electricity meter will run slower, or even run backwards when the sun shines.

De production per solar panel

In the Netherlands, an optimal placed solar panel (facing south, with a slope of 30 to 40 degrees) of 100 Wp will produce about 80 kWh. If the panel is places in an another position, the production won't drop dramatically in most cases.

Share of our own production in our total electicity use

An average household uses about 3800 kWh per year. We use about 2500 kWh per year (family with two children). The eight solar panels (together 1100Wp) have an average annual production of about 780 kWh. This is about 30% of our own electricity requirement.

The production of the PV system

The Figure shows the production for 2003. Up to october 2003 600 Wp was installed, after that time 1100 Wp. The red stripes indicate the calculated production for 600 Wp, the orange columns the measured production (up to october 2003: 600 Wp, and 1100 Wp after october 2003).

The figure below shows our energy requirement. In the summer of 2003 the production of four PV panels (600 Wp) is about half of our total electricity consumption. In our holidays the PV-system produced just a bit more than the requirement of the refrigerator and a number of (smaller) electrical equipment which are always 'on'. After October 2003 500 Wp is added to the 600 Wp system, which was disconnected between June 2004 and January 2005 (see above).

Financial benefits

Smaller PV systems (up to a production of 3000 kWh/year)

As mentioned before, the solar panels ' pump' electricity into the grid, the electricity meter will run slower, or even run backwards when the sun shines. For smaller PV systems you get for every self-produced kWh the price you would pay the electricity company, which is about 23 eurocent per kWh (energy prices: 2008). For PV systems with more than 600 Wp, you have to install a separate group, with a separate fuse. A certified fitter has to install the extra fuse. The costs of this installation are relatively high.

PV (solar electricity) or solar water heater ?

The best choice, a solar water heater, or solar electricity (PV), depends on several aspects. Below I describe some of these aspects.

Costs

A set of 4 PV solar panels (700 Wp) costs about 3500 euro (2008), including installation and mounting materials. In 2008 the Dutch government introduced a bonus of 33 ct/kWh produced by new systems, for 15 years of its lifetime.

A solar water heater costs about 2.500 euro. Together with a new central heating system, you will have to pay 4.000 to 5.000 euro. From september 2008 there are new Dutch subsidies for solar water heaters.

Space

Both systems require space on the roof. In general, PV solar panels are smaller (about 1 m2 per panel) then the collector of a solar heating boiler (about 3 m2).

In the house the PV system requires a negligible amount of space for the inverters and an electricity outlet to make a connection to the grid.

A solar heating boiler requires much more space in the house. A relatively large reservoir for the heated water is required. Also two pipes between the reservoir and collector and a connection to the central heating is required. All parts of the systems have to be placed as close as possible to eachother.

Installation

PV solar panels can be mounted on the roof by yourselves. Also, for smaller systems (smaller than 600 Wp, about 5 m2) the electrical installation can be made by yourselves. If the system is larger, the electrical connection to the grid must be made (or examined) by a certified fitter.

A solar water heater can not be easely installed by yourselves. The collector is larger and a connection to the central heating system has te bo made. In most cases a fitter is required. Also the central heating system has to be suitable for a solar water heater.

Energy production per square metre roof

If your roof is not too large, and you want to save maximal on your (primary) energy requirement, choose the maximal efficiency per m2 roof.

A 100 Watt peak optimal placed PV solar panel (about 0,85 m2) produces in the Netherlands on average 76 kWh per year. This is about 90 kWh per m2 per year. To produce 90 kWh, a power station needs 0.9 GigaJoule (GJ) primary energy. This is about 30 m3 natural gas. A solar water heater with a collector of 2,8 m2 produces About 3 GJ per year. Per square metre roof 1,1 GJ is produced, about 35 m3 natural gas. The solar water heater produces per square metre roof a bit more energy, but the difference is quite small.

Measuring the production

The actual production of solar panels can be measured quite easy with a kWh meter.

The actual production of a solar water heater is quite difficult to measure. Besides the quantity of warm water, also the difference in temperature between the in and out going water has to be measured. Leon Bruinen from SolSolutions points at a meter which measures the amount of energy by taling into account the difference in temperature and the volume. This kinds of meters are also used for accounting the energy use for warm water in apaartment buildings. The meter costs about 2000 euros.