Article. Energy in fokus - from Kyoto to Copenhagen. - AgroTech
Article. Energy in fokus - from Kyoto to Copenhagen. - AgroTech
Article. Energy in fokus - from Kyoto to Copenhagen. - AgroTech
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Jan Hass<strong>in</strong>g, Gartneriernes Fjernvarmeforsyn<strong>in</strong>g,<br />
janhass<strong>in</strong>g@energifyn.jay.net<br />
(organization of producers with district heat<strong>in</strong>g) •<br />
Jan Strømvig, FjernvarmeFyn (Funen district heat<strong>in</strong>g),<br />
js@fjernvarmefyn.dk •<br />
Jens Rystedt, <strong>AgroTech</strong>, jor@agrotech.dk<br />
<strong>Energy</strong> extraction<br />
<strong>from</strong> greenhouse<br />
nurseries with<br />
district heat<strong>in</strong>g<br />
A research project is focus<strong>in</strong>g on how<br />
it is possible <strong>to</strong> use the surplus energy<br />
<strong>from</strong> greenhouses thus mak<strong>in</strong>g the<br />
greenhouse nurseries energy producers<br />
rather than energy consumers<br />
Over a s<strong>in</strong>gle year, a greenhouse<br />
receives more solar energy than it<br />
needs for heat<strong>in</strong>g and controll<strong>in</strong>g humidity.<br />
So, every year there is an energy<br />
surplus <strong>in</strong> a greenhouse. The problem is<br />
just that so far it has not been possible <strong>to</strong><br />
extract the surplus energy and s<strong>to</strong>re it for<br />
later use, for example <strong>from</strong> day until night,<br />
or even better, <strong>from</strong> summer until w<strong>in</strong>ter.<br />
In recent years, new technologies have<br />
made it possible <strong>to</strong> extract surplus energy.<br />
The energy conditions <strong>in</strong> an “average<br />
greenhouse” can be outl<strong>in</strong>ed as below:<br />
When the energy is extracted, it must<br />
be possible <strong>to</strong> either use it immediately<br />
or <strong>to</strong> s<strong>to</strong>re it, for example <strong>in</strong> a groundwater<br />
aquifer or energy s<strong>to</strong>rage ponds.<br />
The <strong>in</strong>vestment required for s<strong>to</strong>rage is very<br />
high, however, and not all locations are<br />
suitable for underground s<strong>to</strong>rage.<br />
The district heat<strong>in</strong>g area around Odense<br />
<strong>Energy</strong> conditions <strong>in</strong> an “average greenhouse”<br />
has 151 greenhouse producers with a <strong>to</strong>tal<br />
of 1.8 million m² under glass. These greenhouses<br />
are all connected <strong>to</strong> the district<br />
heat<strong>in</strong>g network.<br />
An obvious question is whether it is possible<br />
<strong>to</strong> send the surplus energy directly<br />
out <strong>to</strong> the district heat<strong>in</strong>g network, <strong>in</strong>stead<br />
of s<strong>to</strong>r<strong>in</strong>g it <strong>in</strong> expensive seasonal s<strong>to</strong>rage<br />
facilities.<br />
<strong>Energy</strong> for 20.000 households<br />
This year, the district heat<strong>in</strong>g company<br />
on Funen, (Fjernvarme Fyn), Gartnernes<br />
Fjernvarmeselskaber and <strong>AgroTech</strong> are<br />
look<strong>in</strong>g at the possibilities of exploit<strong>in</strong>g<br />
the surplus heat <strong>from</strong> nurseries. Prelim<strong>in</strong>ary<br />
calculations show that the <strong>to</strong>tal potential<br />
energy extraction <strong>from</strong> the nurseries<br />
amounts <strong>to</strong> about 2.2 million GJ per year,<br />
correspond<strong>in</strong>g <strong>to</strong> the energy consumption<br />
of about 20,000 households. However,<br />
KWh per m2 Radiation out<br />
greenhouse per year<br />
1040<br />
Radiation <strong>in</strong>flux <strong>to</strong> a greenhouse 900<br />
<strong>Energy</strong> consumption <strong>in</strong> a greenhouse (standard year) 400 – 450<br />
<strong>Energy</strong> surplus 450 – 500<br />
Potential energy extraction 350 - 400<br />
this assumes that all nurseries extract all<br />
their surplus energy and that the district<br />
heat<strong>in</strong>g network can take all the energy.<br />
The calculations show more realistically<br />
that if 25 percent of the nurseries practice<br />
energy extraction, the district heat<strong>in</strong>g<br />
network will immediately be able <strong>to</strong> take<br />
all the energy without s<strong>to</strong>rage for longer<br />
periods.<br />
Before this can become a reality, however,<br />
there are some technical challenges <strong>to</strong><br />
be overcome - most importantly that the<br />
temperature <strong>from</strong> the energy extraction by<br />
the nurseries is <strong>to</strong>o low <strong>to</strong> be immediately<br />
sent <strong>in</strong><strong>to</strong> the district heat<strong>in</strong>g network. The<br />
temperature must be <strong>in</strong>creased <strong>from</strong> 35°C<br />
<strong>to</strong> about 70°C, us<strong>in</strong>g either solar heat<strong>in</strong>g<br />
plant, heat pumps or the exist<strong>in</strong>g boilers at<br />
the nurseries.<br />
The whole issue of f<strong>in</strong>anc<strong>in</strong>g, costs and<br />
taxation has not yet been resolved.<br />
Nevertheless, the greenhouse companies<br />
do have an energy surplus which could<br />
be recovered and which could transform<br />
greenhouses <strong>from</strong> energy consumers <strong>to</strong><br />
energy producers.<br />
The project is be<strong>in</strong>g funded by Gartneribrugets<br />
Afsætn<strong>in</strong>gsudvalg, a foundation <strong>to</strong><br />
enhance development of the horticultutral<br />
sec<strong>to</strong>r, and will be completed with an<br />
overall analysis at the end of 2009.<br />
<br />
16 ENERGY IN FOCUS