Added imports

GAMS/IntExtOpt.gms

+ 
+ SET all_types crop types including pasture and animal products / cereals, fruits, oilcrops, starchyRoots, treenuts, vegetables, pasture, meat /;
   
- SET crop crop types including pasture / cereals, fruits, oilcrops, starchyRoots, treenuts, vegetables, pasture /;
+ SET commodities(all_types) crop types including pasture / cereals, fruits, oilcrops, starchyRoots, treenuts, vegetables, meat /;
+ SET crop(all_types) crop types including pasture / cereals, fruits, oilcrops, starchyRoots, treenuts, vegetables, pasture /;
  SET crop_less_pasture(crop) arable crops types includes treenuts but not pasture / cereals, fruits, oilcrops, starchyRoots, treenuts, vegetables /;
  SET feed_crop(crop)  / cereals, oilcrops /;
  SET landuse land use type / cropland, pasture /;
      
  PARAMETER previous_area(landuse) areas for previous timestep in ha;
- PARAMETER demand(crop) yield in t per ha;
+ PARAMETER demand(crop_less_pasture) yield in t per ha;
  PARAMETER yield_ref(crop) yield in t per ha;
+ PARAMETER world_input_energy(crop_less_pasture) average input energy from world exports used to determine if we should import or export;
  
  SCALAR meatDemand;
  SCALAR meatEfficency;
+ SCALAR worldMeatInputEnergy
  SCALAR maxLandUseChange;
  SCALAR maxIntensity;
  
 $gdxin %gdxincname%
-$load previous_area, demand, yield_ref, meatDemand, meatEfficency, maxLandUseChange, maxIntensity
+$load previous_area, demand, yield_ref, world_input_energy, meatDemand, meatEfficency, worldMeatInputEnergy, maxLandUseChange, maxIntensity
 $gdxin
                                   
  PARAMETER feedEnergy(crop) energy from feed in MJ per t
          /    cereals       1
               oilcrops      1.5
-              pasture       0.4
-              / ;
+              pasture       0.4 / ;
                             
  VARIABLES
-       area(crop) total area for each crop
-       feedArea(crop)  area used for feed for each crop
-       intensity(crop)  intensity for each crop
-       yield(crop) yield per area for each crop
-       unit_energy(crop) energy per area for each crop
-       energy      total input energy;
+       area(crop) total area for each crop - ha
+       feedArea(crop)  area used for feed for each crop - ha
+       intensity(crop)  intensity for each crop - unitless
+       yield(crop) yield per area for each crop - t per ha
+       unit_energy(crop) energy per area for each crop - energy
+       importAmount(crop_less_pasture) import of crop - t
+       meatImport meat import - t
+       energy      total input energy - energy;
        
- POSITIVE VARIABLE area, intensity, feedArea;
+ POSITIVE VARIABLE area, intensity, feedArea, importAmount, meatImport;
   
  EQUATIONS
        UNIT_ENERGY_EQ(crop) energy per area
@@ -49,10 +55,10 @@ $gdxin
   
  YIELD_EQ(crop) .. yield(crop) =E= yield_ref(crop) * intensity(crop);
   
- CROP_DEMAND_CONSTRAINT(crop_less_pasture) .. (area(crop_less_pasture) - feedArea(crop_less_pasture)) * yield(crop_less_pasture) =G= demand(crop_less_pasture);
+ CROP_DEMAND_CONSTRAINT(crop_less_pasture) .. (area(crop_less_pasture) - feedArea(crop_less_pasture)) * yield(crop_less_pasture) =G= demand(crop_less_pasture) - importAmount(crop_less_pasture);
   
  MEAT_DEMAND_CONSTRAINT .. meatEfficency*sum(feed_crop, feedEnergy(feed_crop) * feedArea(feed_crop) * yield(feed_crop)) + 
-  			feedEnergy('pasture') * area('pasture') * yield('pasture') =G= meatDemand;
+  			feedEnergy('pasture') * area('pasture') * yield('pasture') =G= meatDemand - meatImport;
   
  MIN_INTENSITY_CONSTRAINT(crop) .. intensity(crop) =G= 1;
   
@@ -64,7 +70,7 @@ $gdxin
   
  AGRI_LAND_CHANGE_CONSTRAINT .. abs(sum(crop, area(crop)) / sum(landuse, previous_area(landuse)) - 1) =L= maxLandUseChange;
   
- ENERGY_EQ .. energy =E= SUM(crop, area(crop)*unit_energy(crop));
+ ENERGY_EQ .. energy =E= SUM(crop, area(crop)*unit_energy(crop)) + sum(crop_less_pasture, importAmount(crop_less_pasture) * world_input_energy(crop_less_pasture) + meatImport * worldMeatInputEnergy);
   
  MODEL LAND_USE /ALL/ ;
  SOLVE LAND_USE USING DNLP MINIMIZING energy;

src/ac/ed/lurg/GamsTest.java

@@ -53,8 +53,17 @@ public class GamsTest {
 		parm.addRecord("vegetables").setValue(1);
 		parm.addRecord("pasture").setValue(0.7);
 		
+		parm = db.addParameter("world_input_energy", 1, "average input energy from world exports used to determine if we should import or export energy per t");
+		parm.addRecord("cereals").setValue(0.5);
+		parm.addRecord("fruits").setValue(2.0);
+		parm.addRecord("oilcrops").setValue(2.0);
+		parm.addRecord("starchyRoots").setValue(0.3);
+		parm.addRecord("treenuts").setValue(2.0);
+		parm.addRecord("vegetables").setValue(2);
+		
 		db.addParameter("meatDemand", 0, "demand for meat milk and eggs").addRecord().setValue(160);
 		db.addParameter("meatEfficency", 0, "efficency of converting feed and pasture into animal products").addRecord().setValue(0.1);
+		db.addParameter("worldMeatInputEnergy", 0, "world average meat export energy").addRecord().setValue(3);
 		db.addParameter("maxLandUseChange", 0, "max rate of land use change").addRecord().setValue(0.1);
 		db.addParameter("maxIntensity", 0, "max intensity which will rise over time").addRecord().setValue(3);