Innovations in Danish and German Cities
Brannon Andersen, Emil Morhardt, Bill Ranson
This set of observations is based on a trip from May 23 to June 4, 2011, to Denmark and Germany, funded by the Mellon Foundation, to examine the sustainability practices and infrastructure of northern Europe. This report is one of several covering various aspects of sustainability activities we observed. The trip was remarkable for the variety of small and large-scale power facilities and energy-saving approaches that were discussed, and in many cases visited in the company of local experts. The high urban population density in the Danish and German cities we visited, combined with the stringent open space and agricultural zoning in the urban fringe, are not so common in the U.S., and are partially responsible for the novel approaches we experienced. Much of the remainder of the responsibility is a considerably higher sensitivity to the near-future shortages of fossil fuels, particularly in Denmark where oil, a main economic driver is past peak with yields declining yearly and no other in-country energy sources of any significance other than wind and solar power. This, combined with a very strong desire on the part of planners to decrease the national carbon footprints, has led to much experimentation. In Germany, the nuclear crisis at the Fukushima Daiichi nuclear power plant has created a crises of confidence in German nuclear plants as well; German government has decided in the last few days to phase out nuclear power by 2022 and not restart the 8 nuclear plants shuttered in mid May. It will clearly be necessary to increase the German share of renewable—now targeted to 35% by 2020— because last year nuclear power supplied 23% of Germany’s electricity.
Unlike in the U.S. where much of the development and prototyping is done out of sight in entrepreneurial startups, and in university and national laboratories, the prototypes in Europe seem more likely to be deployed in functional buildings, or integrated into the local infrastructure where they can be viewed by anyone interested. Similarly, utility scale facilities are often cited remotely from normal commerce in the U.S., but few such places exist in Europe, so most facilities are highly visible and unusually approachable.
What follows is a discussion of the types of facilities we visited, and what we learned about the economic and societal factors driving them. We also comment on the existence of similar facilities in the U.S. and on the probability of increasing numbers of them based on our previous experience.
Large wind turbines are visible in many locations in Denmark and Germany. Visitors to the Little Mermaid, Copenhagen's famous city symbol, can, if they raise their gaze a little, see a large array of both nearshore and land-based wind turbines. In Germany it is frequently possible to see a few large turbines spread in small arrays across the countryside. Our clear impression is that, unlike in the U.S., the wind is relatively uniformly distributed and that scaling up with more turbines is not dependent on identifying a few prime locations and maximizing density: rather they can be added at will wherever they are societally acceptable. In other words, as oil is depleted in Denmark, the large quantities of turbine blades stored at power facilities (in downtown Aarhus, for example), can be immediately put to use. In Germany, as economic or carbon footprint needs dictate, they can be added to fields across the countryside, with little evident effect on land use. We have not seen estimates of the total amount of wind power that is feasible in either country, but it is clear that the surface has barely been scratched.
Large scale hydroelectric plants at locks and dams were visible on the Rhine when we walked to France, but we would guess that most such opportunities have long since been utilized. More interesting were the small and ultra small facilities we saw in Freiburg. One, in Vauban, was just a 5 m water wheel with a 1.3 m drop, on a small canal, but it evidently served the needs of many local houses. Another, evidently larger unit apparently using a different kind of turbine, produced a pleasant white noise outside our hostel window. Badenova energy (www.badenova.de) has installed about 15 small hydro installations around Freiburg, and there are probably many more at small hydraulic drops all over Germany, and The idea of a small hydro project in the middle of a residential neighborhood seems foreign indeed in the U.S., but there are doubtless many locations in which they could be employed.
Photovoltaic panels are less frequent in Denmark than in Germany, in part because smaller amounts of sunshine makes wind a more cost-effective strategy in much of Denmark. They are, however, visibly abundant in Freiburg which is at the southern extent of Germany, and many have evidently been in place for a decade or more. We visited an early solar demonstration house with a sun-tracking array of photovoltaics, but more common were vertical arrays on building facades (inefficient we would imagine), standard installations on residential roofs, some buildings in which the entire roof comprised photovoltaics, and most surprising, a long stretch of four-lane highway south of Freiburg with a photovoltaic roof over two of the lanes. The general deployment of photovoltaics was much more extensive in and around Freiburg than we have seen in any U.S. cities, and we passed by the headquarters of a rapidly growing photovoltaic manufacturer in Vauban. Additionally, we know of research at Risø DTU, the Danish National Laboratory for Sustainable Energy in Roskilde between Copenhagen and Aarhus, by one of our colleagues, David Tanenbaum, at Pomona College, on high efficiency organic photovoltaics which are likely to displace the much more expensive crystalline silicon panels that are the standard at the moment.
Solar Water Heating
Also common in Freiburg were standard solar thermal hot water panels on many roofs, and a type of linear panel consisting of evacuated 3 inch glass tubing with a central copper water pipe equipped with radiant fins painted black to intercept sunlight. The vacuum left the tubes cool to the touch, even though the internal tubes got quite hot. This system is often mounted along railings to provide domestic hot water.
Combined Heat and Power (CHP)
CHP, or combined generation ["co-gen"], uses the heat rejected by steam power plants or other combustion-based electricity generation plants to heat water for low-grade energy, such as district heating (see below). Steam power plants consist of boilers in which coal, oil, natural gas, or biomass is burned, (or nuclear fission is allowed to proceed under controlled conditions in nuclear power plants, or parabolic solar troughs or other solar concentrators are used to heat a working fluid whose heat is then transferred to water) to make steam. The steam drives a turbine connected to an electric generator, which produces alternating current electricity for industrial or domestic purposes. At the output of the turbine the steam is cooled by a condenser to lower the temperature and pressure across the turbine, increasing its efficiency. The water flowing through the condenser often comes from surface waters and the heat is just wasted by heating the river, lake, or ocean beside which the plant is located, often with adverse biological consequences. Alternatively some of the heat is dispersed to the atmosphere through a combination of convection and evaporation in cooling towers, such as those often visible at nuclear power plants.
In a co-gen plant this heat that is useless for generating electricity, but useful for industrial process heat or space heating, is captured and used. A common use is district heating in which the heated water is pumped to buildings that can use it for space and water heating.
Cogeneration need not be at a utility scale. In Vauban we examined two much smaller co-gen plants, both consisting of internal combustion engines that could burn multiple fuels. One, an apartment building sized unit, had an engine big enough to operate a medium sized ship. The second, which served a district of several large apartment buildings had the largest internal combustion engine we have seen...ocean liner size we'd guess...with a supplemental boiler to burn wood chips from the Black Forest. Both units had large insulated water tanks associated with them to provide heat storage when the plant wasn't running.
Whereas it is obvious that using waste heat from large power plants is a good idea if the cost of maintaining the district heating pipes isn't prohibitive, it is much less clear that distributed steam generation solves any environmental or economic problem. If localized district heating is the objective than boilers as efficient as the CHP units could be utilized. All the facilities we visited were on the electrical grid so electricity supply was not an issue, and it is unlikely that the small generators are as efficient as the utility-scale ones. We didn't get satisfactory answers onsite, so the concept of distributed co-gen needs further analysis.
In both Denmark and Germany district heating is extensive and common. Our timing in Copenhagen coincided with a major renovation of the district heating system and major streets were being excavated to replace worn pipe. The new pipes were about a foot in diameter, and insulated with about 2 inches of foam before being buried in sand beneath the roadways. Smaller insulated pipes branched off to individual buildings. The pipes contain hot water, piped as much as 35 km (in the case of Aarhus) from a steam power plant. The metering system at individual apartments takes both water flow and temperature into consideration for billing purposes.
Source of Fuels
In Denmark the economy is driven by North Sea oil, but it is well past peak and declining. Denmark is trying to reinvent itself as the alternative fuel center, chiefly because of it's potential for wind power and perhaps various forms of wave and tidal power. Its desire to end its dependence on fossil fuels, however, has led it to base much of it's electrical generation on wood chips shipped in from Poland or Australia, or other distant places. This is unconvincing as a sustainable philosophy to us. Freiburg's use of wood chips as waste from Black Forest forestry is more sensible. Biogas is making headway in both countries. In Germany there are about 4,500 installations converting household waste, manure, and plant debris into methane and compost, obviating much of the need for landfills, a good thing indeed, but there is likely nowhere near enough biogas being produced to substantially alter either Germany's or Denmark's dependence on Russian natural gas from Gazprom. Germany's decision (during our trip) to eschew nuclear power, doesn't help. The only way either country is likely to become independent of fossil fuels any time soon is by a substantial curtailment of energy use.
The Feasibility of Decreasing Energy Use
Comprehensive public transportation in both countries obviates the need for a family car by many. Coupled with intensive urban bicycle use, and ready availability of shared automobiles (in Freiburg at least) one could expect a much lower transportation fuel intensity than in the U.S. But since these features of public life seem already to be fully in place there may be little room for further fuel saving except by wider adoption of electric and hybrid electric vehicles, which seems likely to happen worldwide in any case. This leaves heating and lighting as the main potential sources of conservation.
Insulation and Passive Heating
Finally, we visited a number of developments in Freiburg that were semi-experimental implementations of highly energy-efficient housing. They included south-facing glass walls, internal baffles, triple glazing, heat exchangers on ventilation, and a variety of other structural variants, making it clear that there are considerably more options than we commonly see in the U.S.
Northern Europe is an excellent place to view a variety of energy production and energy-saving practices, particularly those associated with cold climates.