Posts Tagged Renewable Energy

Electric Trucks, Renewable MLPs, and Heat Pumps

A few more of my pieces have run on EarthWise, a 2 minute radio program on WAMC radio in the Northeast.  Here are links:

All are read by the Cary Institute’s Bill Schlesinger.

I got involved with this by volunteering with the Institute.  If you’re near Millbrook, NY, the Cary Institute has regular free lectures on the science of the environment that are well worth attending.  But make sure to get there early- not only for free cookies and coffee, but because they tend to fill up pretty quickly.

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The Cost of Transmission

Tom Konrad, Ph.D.

I’ve been reading a report out of the Colorado Governor’s Energy Office called The REDI Report: Connecting Colorado’s Renewable Resources to the Markets in a Carbon-Constrained Electricity Sector.  I summarized the REDI report’s main conclusions and drew some conclusions for stock market investors here.

I found the report’s discussion of transmission costs particularly interesting, because I’ve had trouble finding numbers for the cost of transmission in the past.  I once resorted to Wikipedia in order to find costs for transmission when comparing them to the costs of large scale electricity storage.  If you don’t think that the two are comparable, consider that long distance transmission can reduce the net variability of wind and solar, making it possible to integrate these renewable forms of generation without the cost of expensive storage.  That’s why even net-zero electricity homes are connected to the grid: it’s prohibitively expensive to buy enough batteries to keep the lights on 24/7.

Here are a couple cost charts from the report:

I took the data from the above table, and plugged it into my spreadsheet comparing the costs of electricity storage.  Below are the updated graphs (click for enlarged versions.)  The notation "2-500 kV AC" means a Double-circuit 500 kV AC line.  As in the storage comparison, I computed the costs and round-trip electricity losses for a 1000 mile line, since that was the example I used in my original Transmission/Storage comparison.

 

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“Heretic” Battles Straw Man

Energy Self-Reliant States [pdf], a flawed study on local Renewable Energy availability from the Institute for Local Self-Reliance (ISLR) found that 18 of the 50 states could not meet their electricity needs with local renewables.   In fact, no state can meet its electricity demand through local renewables without expensive electricity storage.  On a national basis, such storage would cost an estimated $13 Trillion, or over 65 times the cost of the transmission investments they oppose.

by Tom Konrad, Ph.D.

Straw Man: "Transmission is Only for Utility Scale Renewables"

Image: GE Smart Grid Scarecrow (video)

One of the study authors, John Farrell, has been promoting the study as a "Heresy on Transmission."  Rather than a heretic attacking misguided establishment shibboleths, this flawed study attacks a simplistic misunderstanding of why we need transmission.  Farrell and his co-author David Morris are either intentionally promoting this misunderstanding as a straw man, or if they simply fail to grasp the reasons behind long distance transmission’s necessity.

Their straw man is the false choice between states relying on local renewables such as PV on rooftops which supposedly would require only "minimal transmission upgrades" and far-off wind farms requiring expensive long distance transmission.  They say, for example,

[I]f Ohio’s electricity came from North Dakota wind farms — 1,000 miles away — the cost of constructing new transmission lines to carry all that power and the electricity losses during transmission could result in an electricity cost to the consumer that is about the same, or higher, than local generation with minimal transmission upgrades.

This ignores most of the benefits which would flow from new transmission lines connecting North Dakota and Ohio.  A 1,150 mile transmission line from Bismark to Cincinnati would also connect Fargo, Minneapolis, Eau Claire, Madison, Chicago, and Indianapolis running along Interstate Highway corridors (Google maps.)  It also ignores the study’s own finding that Ohio would only be able to generate 29% of the electricity it needs with local renewables. 

Incidentally, their national map shows Ohio being able to generate 33% of its electricity from local renewables, but adding up their own numbers for the renewables they identify gives 29%.  I looked closely at their numbers for only six states, so there may be other arithmetic errors as well.

The states along this hypothetical route are North Dakota, Minnesota, Wisconsin, Illinois, Indiana, and Ohio.  The study found that these states can generate the following percentages of local demand with in-state renewables:

State %Wind % Solar % Small hydro % CHP Total
North Dakota 14,000% 19% 1% 4% 14,024%
Minnesota 1,311% 24% 1% 4% 1,340%
Wisconsin 120% 22% 1% 5% 150%
Illinois 57% 17% 2% 4% 80%
Indiana 83% 18% 1% 3.6% 106%
Ohio 3% 20% 1% 5% 29%

If each of these states attempted to meet their local electricity needs with the renewables in the study, Ohio and Indiana would still need to import some electricity from other states.  Although Ohio would not need to import power from as far away as North Dakota, they would have to tap into Minnesota’s wind resources if demand were to be satisfied along this corridor.  An attempt to meet that demand with the nearest resources might look like this:

State %Wind % Solar % Small hydro % CHP Total
North Dakota 300% 2% - 2% 304%
Minnesota 150% 10% 1% 2%   163%
Wisconsin 120% 22% 1% 5%   148%
Illinois 57% 17% 2% 4%  80%
Indiana 83% 18% 1% 3%   105%
Ohio 3% 20% 1% 5%  29%

You’ll note that the total above exceeds 600% because the states with renewable energy surpluses have much lower local demand.  The magnitudes of this demand are my best guess.  Keep in mind that I did not choose this corridor to make my example work; the suggestion came directly from the transmission example in the study.

The Consequences of Timing

By the study’s own methodology, both Ohio and Illinois need interstate transmission, because they cannot generate all their renewable electricity locally.  Yet, as I will demonstrate, even though North Dakota and Minnesota would be generating electricity for export, they will often need to import renewable electricity as well.  

Using the Correlation Maximization tool on Energy Timing (note: Energy Timing has been taken down, see comment here.), I generated the best portfolio of North Dakota wind and solar farms to meet the needs of Square Butte Electric Coop, an electric utility in Grand Forks, ND.  The results are shown below:

Composition of Optimal Portfolio of North Dakota Renewable Energy:  ND Optimal Portfolio

  Site Name Type Optimal Weight Capacity Factor
1) Olga 5, ND Wind 63% 21%
2) Pickert, ND Wind 19% 38%
3) Valley City, ND Wind 18% 22%

 

Normalized Diurnal ND wind and demand.png

This combination of three wind farms represents the best fit between electric output from existing wind farms and solar sites in Energy Timing’s database, and local demand.  Even though this is the best fit, the correlation between supply and demand is only 13.2%.  Solar sites do not appear in the optimal portfolio because they do not lead to a better fit.

As you can see from the bottom graph, wind output is strongest in the morning, when demand is relatively low, and falls off in the afternoon, as demand rises.  Hence, unless North Dakota builds far more wind farms than it needs to supply local demand (an expensive proposition which could only be justified by electricity exports), they would not have enough electrify in the afternoon and early evening, when the wind typically dies down.  This would be the situation on a typical day.  On any given day, wind power is even more variable than it is on average, leading to large and frequent swings from oversupply to undersupply.

Composition of Optimal Portfolio of Minnesota Renewable Energy:  MN Optimal Portfolio

  Site Name Type Optimal Weight Capacity Factor
1) International Falls, MN Solar 37% 17%
2) Minneapolis, MN Solar 34% 20%
3) Rochester, MN Solar 23% 19%
4) Duluth, MN Solar 6% 18%

 

Normalized Diurnal MN Solar and demand

In the case of Minnesota electrical demand, solar sites turn out to be a better fit than wind sites.  In reality, if Minnesota were to attempt to meet local demand with renewable energy, a mix of wind and solar sites would be used, since wind is so much less expensive than solar.  But since solar sites are the best fit for local demand, a mix of wind and solar would produce a worse match than the 24.5% correlation we see in the scenario above.

Benefits of Transmission

We can now see how both Minnesota and North Dakota would benefit with a high capacity transmission connection between the states.  In the early morning, before the sun rises, Minnesota will not be producing any domestic renewables, so it makes sense to import electricity from North Dakota, where production is far in excess of demand all morning.  Minnesota will in turn be able to supply excess solar power to North Dakota in the afternoon before the sun gets low and cuts solar output.  

In short, even though both Minnesota and North Dakota can easily produce enough local renewable electricity for their needs, the timing of that electricity causes problems of both oversupply and unmet demand.  If we build transmission connecting states regions, these problems are reduced, and less storage is needed to make up the difference.

As we increase the interregional connections, we will be able to bring in power from farther afield that better meets demand.  For instance, both these states don’t have enough local renewables in the evening, even when combined.  The worst period is just around dusk, from about 5pm to 8pm Central time, before the wind begins to pick up at night in North Dakota.  But in the sunny Mojave Desert of southern California, the sun is still up (it’s two hours earlier, Pacific Time), and large Concentrating Solar Power (CSP) plants can use relatively cheap thermal storage to continue producing power for hours after sunset.

We can also see that both North Dakota and Minnesota typically have spare production capacity in the summer months, so they could export electricity back to the Southwest during these months, when Southwest electricity demand peaks due to air conditioning loads.

As we increase the length of regional transmission networks, each state along the path gains, both as an electricity exporter and as an importer depending on the season and weather conditions.  Ohio does not need to pay for giant transmission lines from North Dakota to import which "could result in an electricity cost to the consumer that is about the same, or higher, than local generation."  North Dakota, Minnesota, Wisconsin, Illinois, and Indiana would also benefit from such a line, and all could be asked to contribute.

Costing Storage vs. Transmission

The study’s authors also invoke electricity storage to "solve" the problem of timing, saying

Some renewable fuels, like sunlight and wind, are variable.  Thus, the estimates, especially for wind, assume a significant level of storage or on-demand distributed generation.

Unfortunately, they make no attempt to account for the price tag of such storage.  They state only, 

This report does not examine storage and its implications, but in our analysis of variable renewable energy potential, we assume that sufficient storage is available.

"On-demand distributed generation" could come from natural gas or biomass.  Renewable generation relies on the availability of the natural resource, few of which can be stored.  Even incremental hydropower is typically not on-demand, because it is usually the result of adding generation to existing dams and comes with obligations to maintain flow rates.

Biomass based power is typically baseload, not on-demand.  Furthermore, the study authors explicitly rule out the large scale use of biomass for electricity because they expect the amount of biomass-based electricity to be "modest."  Even if large scale, on-demand distributed biomass based generation were available, it would only be available in those states with a large biomass resources.  See the map below.

Natural gas is an incomplete response to climate change in that it is a fossil fuel, may not even be available in the necessary quantities, and must be imported by the vast majority of states.  What is the point in pushing for reliance on locally generated renewable electricity if it only increases our dependence on imported natural gas which may not be available and produces greenhouse gas emissions? 

Given the not only daily, but seasonal mismatches between local electricity production and demand, states which are locally self-sufficient in electricity would have to invest in a month or more worth of storage.  While electric vehicles may be able to provide some daily or hourly storage, they will not be available for seasonal electricity storage, since the vehicle owners will need to drive them, and so cannot keep them fully charged for months or even days on end.

The cheapest large scale electricity storage solutions, (Pumped Hydropower, Compressed Air Energy Storage, and Molten Salt Thermal Storage) typically cost $10 to $50 per kWh of storage.  Unfortunately, all three of these options are limited in where they can be located, so restricting transmission will also restrict the use of these cheaper forms of storage.  The cheapest battery and flow battery storage technologies cost about $100 to $150 per kWh.  To be generous, I will assume that all states can build as much electricity storage as they want at $50 per kWh, or $50,000 per MWh.  I will also assume that geothermal, hydropower, combined heat and power, and efficiency gains will mean that solar and wind will need to supply only 50% of our current electricity usage. 

According to the Energy Information Administration, total electricity production in 2007 was 4,156,745 thousand MWh.  An average monthly production was thus 346,395,000 MWh, and the cost of a month’s worth of national electricity storage to meet half of a month’s demand would be $8,665 Billion under the assumptions above.  In contrast, the ILSR study states that "FERC, Congress, and environmental groups… rush to accelerate the construction of a new $100-$200 Billion interregional transmission network."  

If such a network cost $200 Billion, and reduced the need for storage by only 10%, then it would have paid for itself more than eight times.  Given less conservative (and I think more realistic) assumptions of reducing the need for storage by 50%, and a per MWh cost of storage of $75,000, a regional transmission network would pay for itself in reduced storage needs by 65 to 1.

Conclusion

To me, 65-to-one, or a savings of approximately $13 Trillion, seems worth the price of stringing wires.  For comparison, $700 Billion has been spent on the war in Iraq since 2001.  In other words, the ILSR study is suggesting that we pay for eighteen wars in Iraq in order to avoid building an interregional transmission network, costing about as much as we spent in Iraq in 2008. 

In fact, the price for local self-reliance on renewable energy would likely be higher.  Thirteen trillion dollars does not include the cost savings that the report’s authors tried to address: Transmission allows us to exploit less expensive renewable generation.    Furthermore, the variability of both wind and solar generation can be vastly reduced by combining the output of dispersed wind and solar farms.  Less variability reduced the need for costly spinning reserves to stabilize the grid if wind power suddenly drops or a cloud passes above a solar farm.

Not all self-styled heretics are fighting a just cause against an oppressive consensus.  To the extent that a consensus exists in favor of an improved national transmission grid, it is based on sound science and economics.  It is unfortunate that so many environmentalists are seduced by the mirage of renewable energy self-reliance.

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Managing the Peak Fossil Fuel Transition 

EROI and EIRR

by Tom Konrad, Ph.D.

Current renewable energy technologies must be adopted in conjunction with aggressive Smart Growth and Efficiency if we hope to continue our current standard of living and complex society with diminished reliance on fossil fuels. These strategies have the additional advantage that they can work without large technological breakthroughs. 

Energy Return on Investment

Energy keeps our economy running.  Energy is also what we use to obtain more energy.  The more energy we use to obtain more energy, the less we have for the rest of the economy.  

The concept of Energy Return on Investment (EROI), alternatively called Energy Return on Energy Invested (EROEI) has been widely used to quantify this concept.  The following chart, from a SciAm paper, shows the EROI of various sources of energy, with the tan section of the bar representing the range of EROIs depending on the source and the technology used.  I’ve seen many other estimates of EROI, and this one seems to be on the optimistic (high EROI) end for most renewable energy sources.

The general trend is clear: the energy of the future will have lower EROI than the energy of the past.  Low carbon fuels such as natural gas, nuclear, photovoltaics, wind, and biofuels have low EROI compared to high-carbon fuels such as coal and (formerly) oil.   

The graph also clearly shows the decline in the EROI over time for oil.  Other fossil fuels, such as coal and natural gas, also will have declining EROI over time.  This happens because we always exploit the easiest resources first.  The biggest coal deposits that are nearest to the surface and nearest to customers will be the first ones we mine. When those are depleted, we move on to the less easy to exploit deposits.  The decline will not be linear, and new technology can also bring temporary improvements in EROI, but new technology cannot change the fact that we’ve already exploited all the easiest to get deposits, and new sources and technologies for extracting fossil fuels often fail to live up to the hype.

While there is room for improvement in renewable energy technologies, the fact remains that fossil fuels allow us to exploit the energy of millions of years of stored sunlight at once.  All renewable energy (solar, wind, biomass, geothermal) involves extracting a current energy flux (sunlight, wind, plant growth, or heat from the earth) as it arrives.  In essence, fossil fuels are all biofuels, but biofuels from plants that grew and harvested sunlight over millions of years.  I don’t think that technological improvements can make up for the inherent EROI advantage of the many-millions-to-one time compression conveys to fossil fuels.

Hence, going forward, we are going to have to power our society with a combination of renewable energy and fossil fuels that have EROI no better than the approximately 30:1 potentially available from firewood and wind.  Since neither of these two fuels can come close to powering our entire society (firewood because of limited supply, and wind because of its inherent variability.) Also, storable fuels such as natural gas, oil, and biofuels all have either declining EROI below 20 or extremely low EROI to begin with (biofuels). Energy storage is needed to match electricity supply with variable demand, and to power transportation. 

Neither hydrogen nor batteries will replace the current storable fuels without a further penalty to EROI.  Whenever you store electricity, a certain percentage of the energy will be lost.  The percent that remains is called the round-trip efficiency of the technology, shown on the vertical axis of the graph below, taken from my earlier comparison of electricity storage technologies. (Click to enlarge.)

Storage Technology Comparison

Round trip efficiency (RTE) for energy storage technologies is equivalent to EROI for fuels: it is the ratio of the energy you put in to the energy you get out.  You can see from the chart, most battery technologies cluster around a 75% RTE.   Hence, if you store electricity from an EROI 20 source in a battery to drive your electric vehicle, the electricity that actually comes out of the battery will only have an EROI of 20 times the RTE of the battery, or 15.  Furthermore, since batteries decay over time, some of the energy used
to create the battery should also be included in the EROI calculation, leading to an overall EROI lower than 15.

The round trip efficiency of hydrogen, when made with electrolyzers and used in a fuel cell, is below 50%, meaning that, barring huge technological breakthroughs, any hoped-for hydrogen economy would have to run with an EROI from energy sources less than half of those shown.

Taking all of this together, I think it’s reasonable to assume that any future sustainable economy will run on energy sources with a combined EROI of less than 15, quite possibly much less. 

It’s Worse than That: The Renewables Hump

All investors know that it matters not just how much money you get back for your investment, but how soon.  A 2x return in a couple of months is something to brag about, a 2x return over 30 years is a low-yield bond investment, and probably hasn’t even kept up with inflation.

The same is true for EROI, and means that users of EROI who are trying to compare future sources of energy with historic ones are probably taking an overly-optimistic view.  For fossil fuels, the time we have to wait between when we invest the energy and when we get the energy back in a form useful to society is fairly short.  For instance, most of the energy that goes into mining coal comes in the digging process, perhaps removing
a mountaintop and dumping the fill
, followed by the actual digging of the coal and shipping it to a coal plant.  Massey Energy’s 2008 Annual Report [pdf] states that "In 2008… we were able to open 19 new mines, and ten new sections at existing underground mines."  This hectic rate of expansion leads me to believe that the time to open a new mine or mine section is at most 2 years, and the energy cycle will be even quicker at existing mines, when the full cycle between when the coal is mined and when it is burnt to produce electricity requires only the mining itself, transport to a coal plant, and perhaps a short period of storage
at the plant.  Most coal plants only keep a week or two supply of coal on hand.

In contrast, Nuclear and Renewable energy (with the exception of biofuels and biomass) present an entirely different picture.  A wind farm can take less than a year to construct, it will take the full farm life of 20 years to produce the 10 to 30 EROI shown in the graph.  Solar Photovoltaic’s apparent EROI of around 9 looks worse when you consider that a solar panel has a 30 year lifetime.  Only a little of the energy in for Nuclear power comes in the form of Nuclear fuel over the life of the plant: most is embodied in the plant itself.   

Jeff Vail has been exploring this concept on his blog and the Oil Drum.  He refers to the problem of the front-loading of energy investment for renewable energy as the Renewables Hump.  He’s also much more pessimistic than the above chart about the actual EROI of most renewables, and found this chart from The Economist which illustrates the up-front nature of the investment in Nuclear and Wind: 

In terms of EROI timing, those technologies for which the cost of generation includes more fuel have an advantage, because the energy used to produce the fuel does not have to be expended when the plant is built.

In a steady state of technological mix, EROI is the most important number, because you will always be making new investments in energy as old investments outlive their useful lives and are decommissioned.  However, in a period of transition, such as the one we are entering, we need a quick return on our energy investments in order to maintain our society.  Put another way, Jeff Vail’s "Renewables Hump" is analogous to a cash-flow problem.  We have to have energy to invest it; we can’t simply charge it to our energy credit
card and repay it later.  That means, if we’re going to keep the non-energy economy going while we make the transition, we can’t put too much energy today into the long-lived energy investments we’ll use tomorrow.

To give a clearer picture of how timing of energy flows interacts with EROI, I will borrow the concept of Internal
Rate of Return (IRR)
from finance.  This concept is covered in any introductory finance course, and is specifically designed to be used to provide a single value which can be used to compare two different investments with radically different cash flow timing by assigning each a rate of return which could produce those cash flows if the money invested were compounded continuously.

Except in special circumstances involving complex or radically different size cash flows, an investor will prefer an investment with a higher IRR.

Energy Internal Rate of Return (EIRR)

I first suggested that IRR be adapted to EROI analysis by substituting energy flows for investment flows in early 2007.  I called the concept Energy
Internal Rate of Return, or EIRR
.  Since no one else has picked up the concept in the meantime, I’ve decided to do some of the basic analysis myself.

To convert an EROI into an EIRR, we need to
know the lifetime of the installation, and what percentage of the energy cost is fuel compared to the percentage of the energy embodied in the plant.  The following chart shows my preliminary calculations for EIRR, along with the plant lifetimes I used, and the EROI shows as the size of each bubble.

 EIRR

The most valuable energy resources are those with large bubbles (High EROI) at the top of the chart (High EIRR.)  Because of the low EIRR of Photovoltaic, Nuclear, and Hydropower, emphasizing these technologies in the early stage of the transition away from fossil fuels is much more likely to lead to a Renewables Hump scenario in which we don’t have enough surplus energy to both make the transition without massive disruption to the rest of the economy.

How to Avoid a "Renewables Hump"

Note that the three fossil fuels (oil, gas, and coal) all have high EIRRs.  As we transition to lower carbon fuels, we will want to keep as many high EIRR fuels in our portfolio as possible. 

The chart shows two renewables with EIRRs comparable to those of fossil fuels: Wood cofiring, and Wind.  Wood cofiring, or modifying existing coal plants to burn up to 10% wood chips instead of coal was found to be one of the most economic ways of producing clean energy in the California RETI study. The scope for incorporating biomass cofiring is fairly limited, however, since it requires an existing coal plant (not all of which are suitable) as well as a local supply of wood chips.  Some coal plants may also be converted entirely to wood, but only in regions with plentiful supplies of wood and for relatively small plants.  The EIRR for this should fall somewhere between Wood cofiring and Wood Biomass, which is intended to represent the cost of new wood to electricity plants.

Natural Gas

To avoid a Renewables Hump, we will need to emphasize high-EIRR technologies during the transition period.  If domestic natural gas turns out to be as abundant as the industry claims (there are serious doubts about shale gas abundance,) then natural gas is an ideal transition fuel.  The high EIRR of natural gas fired generation arises mostly because,
as shown in the chart "it’s a gas" most of the cost (and, I assume energy investment) in natural gas generation is in the form of fuel.  Natural gas generation also has the advantage of being dispatchable with generally quick ramp-up times.  This makes it a natural complement to the variability of solar and wind.

However, I think it is unlikely that we’ll have enough domestic natural gas to both (1) rely much more heavily on it in electricity generation and (2) convert much of our transportation fleet to natural gas, as suggested by T Boone Pickens.  We’re going to need more high-EIRR technologies to manage the transition.  Fortunately, such technologies exist: the more
efficient use of energy.  

Energy Efficiency and Smart Growth

I have been unable to find studies of the EROI of various efficiency
technologies.  For instance, how much energy is embodied in insulation, and how does that compare to the energy saved?  We can save transportation fuel with Smart Growth strategies such as living in more densely populated areas that are closer to where we work, and investing in mass transit infrastructure. 
The embodied energy of mass transit can be quite high in the case of light rail, or it can be very low in the case of better scheduling and incentives for ride sharing.

Many efficiency and smart growth technologies and methods are likely to have much
higher EIRRs than fossil fuels.  We can see this because, while the
embodied energy has not been well studied, the financial returns have. 
Typical investments in energy efficiency in utility run DSM programs cost
between $0.01 and $0.03 cents per kWh saved, much less than the cost of new fossil-fired generation.  This implies a higher EIRR for energy efficiency, because part of the cost of any energy efficiency measure will be the cost of the embodied energy, while all of the savings are in the form or energy.   This relationship implies that higher IRR technologies will generally have higher EIRRs as well.  

Smart growth strategies also often show extremely high financial returns, because they reduce the need for expensive cars, roads, parking, and even accidents [pdf.]

Conclusion: Brian or Brawn

The Renewables Hump des not have to be the massive problem it seems when we only look at supply-side energy technologies.  By looking at demand side solutions, such as energy efficiency, conservation, smart growth, and transit solutions, we need not run into a situation where the energy we have to invest in transitioning from finite and dirty fossil fuels to limitless and clean renewable energy overwhelms our current supplies.  

Efficiency and Smart Growth are "Brain" technologies, as opposed to the "Brawn" of traditional and new energy sources.  As such, their application requires long-term planning and thought.  Cheap energy has led to a culture where we prefer to solve problems by simply applying more brawn.  As our fossil fuel brawn fades away, we will have to rely on our brains once again if we hope to maintain anything like our current level of economic activity.

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Top Five Environmental Stocks for Gifts

For the Shopping season, I’ve just publised an article on a gift that’s greener than just giving more “stuff.” Help your young ones prepare for their future (and the future of the planet) with my Top Five Stocks to Give as Gifts this Holiday Season.
Green Gift

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