SolarByTheWatt.com

Solar Energy Land Area Efficiency or How Many Acres per MW, kWp per Acre

By SolarByTheWatt.com on March 9, 2009

Solar power alongside the applauding it gets it is also being criticized by the opponents of it especially in terms of the different measures of efficiency – physical, economic (investment) and land area use efficiency. Land area use efficiency is the topic of this study. Let’s look at the definito0ns for the other measures of efficiency just to put our essay in proper context.

Physical efficiency for example is the measure of what portion of the light energy is being transformed to useful electric energy. That currently runs for different types of photovoltaic cell technologies between 8 and 30 and by some reports 38%. We will spare a separate article on the different technologies and their respective efficiency readings.

Economic efficiency or investment efficiency is the dollar cost per nominal generating watt power or simply dollar per watt peak ($/Wp). The investment efficiency can be calculated at the different stage of completeness of a solar photovoltaic system or component – cells, panels, installed systems, power stations. We want to dedicate special studies to the importance of these measures of efficiency. Be prepared to hear our opinion that economic, or investment efficiency is much more important to the useful implementation of this technology than physical efficiency is.

Land area use efficiency is the measure of how much land area is needed for certain capacity of nominal (peak) power of a solar photovoltaic power station (or smaller system). The units of measure used are usually:

acres per megawatt or acres per MW – the land area needed in acres per MW of generation; the way to calculate that is to divide the area used in a project in acres by the peak power of the project in MW;

kilowatt per acre or kW per acre – this is the amount of installed peak power in kW (1 MW = 1,000 kW) divided by the land area needed in acres.

The equivalent units of measure used more often overseas (incl. Europe) are using the derivatives of the metric system for land area – hectares (10,000 sq.meters) and decares (1,000 sq.meters) – hectares per MW, decares per MW and kW or MW per hectare or decare.

We wanted to find out what is the approximate land area efficiency of existing completed and planed projects or ones in progress. We looked first at some of the biggest solar photovoltaic projects around the world, tried to find out quoted figures for their peak capacity and land are used and calculate the land are use efficiency for them.

We also looked at publications discussing proposed project especially for technologies that are just emerging.

This is what we found out.

Some of the largest completed solar photovoltaic power plants, also called solar parks or fields, have area efficiency of about 4.5 to 8 acres per MW. This is when crystalline (mono-crystalline or poly-crystalline) technology cells, modules are used. With thin-film technologies the efficiency is about 10 to 13.5 acres per MW.

For comparison we also looked at data for some solar thermal project and we estimated land area use efficiency of about 5 to 11 acres per MW. The lower values were for projects involving Sterling engines as opposed to the more traditional technology of parabolic mirror throws heating oil in a tube.

Here is a table of our calculations with numbers in the other units of measure and also a list of the resources used.

Project No	Project	Capacity, DC Peak Power, Wp. MW	Land Used, hectares, 10,000 m2	Land Used, decares, 1000 m2
1	Olmedilla Photovoltaic Park	60	108	1,080
2	Puertollano Photovoltaic Park	47	150	1,500
3	Amareleja, Moura, Portugal	62	130	1,300
4	Waldpolenz Solar Park	40	220	2,200
5	Sempra Generation near Boulder City, NV	10	32	320
6	PG&E	6.4	64	640
7	Ivanpah	1,300	4250	42,500
8	Southern Ca. Edison, Stirling Eng. Systems	850	1830	18,300
9	Mojave Solar Park	553	2400	24,000

Project No	kWp/decare	kWp/acre	Acre/MW	Notes
1	55.6	224.83	4.45
2	31.3	126.80	7.89
3	47.7	193.00	5.18
4	18.2	73.58	13.59	Thin-film
5	31.3	80.00	12.50	Thin-film
6	10.0	81.00	12.35	Thin-film
7	30.6	123.79	8.08	Solar thermal
8	46.4	187.97	5.32	Sterling Engine
9	23.0	92.17	10.85	Solar Thermal